In an interactive network board, a method and apparatus for preventing inadvertent loading of a programmable read only memory

ABSTRACT

Method and apparatus for loading a ROM image into PROM comprises loading a ROM image into a dynamic random access memory, verifying the accuracy of the ROM image in the dynamic random access memory, and receiving a command to flash EPROM with the stored ROM image. A hardware interlock mechanism is deactivated by a two-step command procedure so as to enable flashing the EPROM. Specifically, a predetermined bit pattern is written to a first predetermined address on an address bus, one bit being latched to cause a flash signal to be output to a transistor switch and to be pre-loaded at a flip flop. A second predetermined address is read from so as to clock the flip flop. The output of the flip flop closes the transistor switch allowing the flash enable signal to reach the EPROM. The EPROM is erased, after which the ROM image is loaded into the PROM.

BACKGROUND OF THE INVENTION

1. Field Of The Invention

The present invention relates generally to a circuit board which iscoupled to a local area network peripheral (e.g. a printer) and whichallows the peripheral to be an intelligent, interactive network membereliminating the necessity of dedicating a personal computer to managethe peripheral. More particularly, the present invention relates to amethod and apparatus for providing an interlock mechanism for preventinginadvertent application of a load enable signal to a PROM, such as whenpower is applied or disconnected from the board.

2. Related Art

Local Area Networks ("LANs") are known for coupling together a pluralityof personal computers with peripheral devices such as printers, copiers,etc., to provide for enhanced communication and shared resources.Heretofore, peripherals such as printers coupled to a LAN were ratherunintelligent, merely accepting information from the LAN and printingsuch information on a hard copy. Moreover, such printers usuallyrequired a host personal computer ("PC") to effectively manage the flowof data to the printer, i.e., to act as a "server" for the printer. Thisalmost always required that the host PC be dedicated solely to theprinter server task.

A number of products have recently appeared which ostensibly eliminatethe need for such a dedicated PC by incorporating hardware and softwareinto a circuit board which may be coupled into the peripheral in orderto perform limited server functions. For example, ASP Computer Products,Inc. provides a device known as "JetLAN/P" which acts as a stand-aloneprint server for Novell networks. The JetLAN/P® device couples to a LANusing a 10Base-2 thin coaxial cable or a 10Base-T twisted-pair cable.However, the JetLAN/P® couples to the printer only through the printer'sparallel port. Thus, while print information can be sent to the printer,the amount of printer status information which can be returned from theprinter is severely restricted. For example, such a device may obtain"off-line" and "out of paper" status from the printer, but little else.Such a device does very little toward making the printer a trulyintelligent, responsive member of the network.

Other known devices for coupling a printer to a LAN include theHewlett-Packard Jet Direct® C2071A/B and C2059A, the Extended SystemsEtherFlex®, the Intel NetPort® and NetPort II®, the Castelle LANPress®and JetPress®, and the MILAN FastPort®. However, all of these devicessuffer from the same disadvantages as the ASP JetLAN in that they do notallow the printer to transmit sufficient amounts of data to the LAN toenable the printer to be an effective and intelligent member of thenetwork.

Interactive peripheral devices, as discussed above, may include aprocessor, a random access memory (RAM) and a programmable read onlymemory (PROM). Due to recent developments in ROM technology, it ispossible to provide interactive peripheral devices with an EPROM whichcan be electrically erased and electrically reprogrammed. The ability toelectrically erase and electrically reprogram is a distinct advantageover the previous technology since PROMs had to be removed from a board,erased with ultra-violet rays and then reprogrammed from a separateprogramming station.

This advantage of electrically erasing and electrically reprogramming aPROM while on a board has not been entirely welcome. That is, an EPROMcan be easily altered by corrupt data sent from a processor duringpower-up or power-down. That is, since most processors utilized todayhave a CMOS technology design, these processors continue to process aspower dissipates upon power-down or starts to process during power-upwith very little power. Because of this, transient data bursts may besent to the EPROM during either an abrupt power-on or power-down. Thesetransient data bursts can easily corrupt a program stored in an EPROM.

Heretofore, it has not been possible to prevent an EPROM from beingloaded with corrupt data. Consequently, when power is removed or appliedto a board, a program within an EPROM can be easily altered.

SUMMARY OF THE INVENTION

The present invention overcomes the drawbacks noted above by providingstructure and function on a circuit board coupled to a peripheral whichwill permit the peripheral to be a responsive, intelligent member of anetwork.

In one aspect, the present invention provides a method for providing ahardware interlock system for preventing inadvertent application of aload enable signal to a PROM. The load enable signal is applied onlyafter a two-step hardware enabling procedure is performed. In the firststep, a predetermined bit pattern is written to a first address, and inthe second step a read is performed from a second address. According tothis aspect of the invention, a method for loading a ROM image into PROMcomprises the steps of loading a ROM image into a DRAM disposed on aninteractive network board, verifying the integrity of the ROM image inDRAM, receiving a command to load the PROM, writing a predetermined bitpattern to a first address and reading from a second address so as toenable a write signal on the PROM, erasing the PROM, and loading the ROMimage into the PROM.

According to another aspect of the invention, an apparatus for loading aROM image into a PROM comprises an address bus, a data bus, and a PROMconnected to the address bus and the data bus, the PROM including a loadenable input. A transistor switch switchably provides a load enablesignal to the load enable input of the PROM. A flip flop controlsswitching actuation of the transistor switch. In response to a firstaddress on the address bus, a latch latches at least one bit from thedata bus, the latch pre-loading the flip flop with the latched bit. ADC/DC converter which is responsive to the latch latching apredetermined bit pattern provides a load enable signal to thetransistor switch. A decoder responsive to a second predeterminedaddress on said address bus clocks the flip flop. A processor outputsthe predetermined bit pattern to the first output address, accesses thesecond output address, erases the PROM, and loads the ROM image into thePROM.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-noted advantages and features of the present invention willbecome more readily apparent from the following detailed description ofthe preferred embodiments when taken in conjunction with the Drawings inwhich:

FIG. 1 is a block diagram of a Local Area Network according to thepresent invention;

FIG. 2 is a block diagram of a plurality of Local Area Networks coupledtogether;

FIG. 3 is a block diagram showing the Network Expansion Board accordingto the present invention coupled between the Local Area Network and theprinter;

FIG. 4 is a block diagram of the Network Expansion Board according tothe present invention;

FIGS. 5A, 5B and 5C comprise a top-level flowchart showing the basicfunctions of the Network Expansion Board according to the presentinvention;

FIG. 6 is a diagram showing the sequence in which software modules areloaded from the Network Expansion Board ROM to RAM;

FIG. 7 is a block diagram showing hardware and software interfacesbetween the LAN and the Network Expansion Board;

FIG. 8 is a flowchart showing how the EPROM firmware is configured forplacing the Network Expansion Board in an operational mode;

FIG. 9 is a chart showing the physical construction of different framepackets used on Ethernet;

FIG. 10 is a flowchart showing the operation of a PRESCAN softwaremodule;

FIG. 11 is a chart showing that the PRESCAN module may be used withother software protocols;

FIG. 12 is a chart for explaining the software structure of theSAPSERVER program;

FIG. 13 is a flowchart showing the operation of SAPSERVER;

FIG. 14 is a flowchart showing the operation of a CPINIT program;

FIG. 15 is a flowchart showing the operation of a CPCONSOL program;

FIGS. 16A and 16B comprise a flowchart showing the operation of aCPSOCKET program;

FIGS. 17A and 17B comprise a flowchart showing the automatic logging ofperipheral statistics;

FIG. 18 is a flowchart showing how multi-tasking processing isperformed;

FIG. 19 is a flowchart showing how to place the printer in a safe,default configuration;

FIG. 20 is a flowchart showing the downloading of executable files tothe Network Expansion Board from the local area network;

FIG. 21 is a flowchart showing the loading of independently-executablemodules in the EPROM of the Network Expansion Board;

FIG. 22 is a block diagram showing Network Expansion Board EPROM flashprotection circuitry;

FIG. 23 is a flowchart showing the operation of the circuitry of FIG.22;

FIG. 24 is a flowchart showing the operation of remotely loadingfirmware in the Network Expansion Board EPROM;

FIG. 25 is a block diagram showing a hardware configuration for testingthe Network Expansion Board; and

FIGS. 26A and 26B comprise a flowchart showing a method of testing theNetwork Expansion Board using the test configuration of FIG. 25.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In its general aspects, the present invention provides hardware andsoftware solutions for making a network peripheral, such as a printer,an interactive network member capable not only of receiving andprocessing data received from the network, but of transmitting to thenetwork significant amounts of data such as detailed status information,operational parameters, and even data input to the peripheral throughother modalities such as scanning, facsimile reception, etc. Byintegrating such hardware and software with the peripheral, it ispossible to eliminate the requirement for dedicating a personal computerto the peripheral to act as a peripheral server.

1. ARCHITECTURE

FIG. 1 is a block diagram showing the present invention incorporatedinto a Network Expansion Board ("NEB") 2 coupled to a printer 4 whichhas an open architecture (to be discussed below). The NEB 2 is coupledto the LAN bus 6 through a LAN interface 8, for example, Ethernetinterfaces 10Base-2, 10Base-T, or 10Base-5, respectively, with a Coaxconnector, an RJ45 connector, or a DB15 connector (AUI). Also coupled tothe LAN 6 may be such network members as PC 10, PC 12, PC 14 (which inthis case acts as the network administrator if the administrator haslogged in at that PC; to be discussed below), and a printer 16 (withembedded QSERVER functionality; also to be discussed below). Other LANmembers may include PC 18 (acting as a print server; to be discussedbelow) with attached printer 20, PC 22 (acting as an RPRINTER; to bediscussed below) with attached printer 24, and printer 26 which iscoupled to the LAN 6 through a NetPort device 28 (discussed in theBackground of the Invention above). A file server 30 is coupled to theLAN 6 and serves as a "library" for files to be transmitted andprocessed on the LAN. The file server 30 may have attached printers 32and 34.

In more detail, the network depicted in FIG. 1 may utilize any networksoftware such as Novell or Unix software in order to effectcommunication among the various network members. The present embodimentswill be described with respect to a LAN utilizing Novell NetWare®software (to be discussed in greater detail in section 3a below)although any network software may be used. A detailed description ofthis software package may be. found in the publications "NetWare® User'sGuide" and the "NetWare® Supervisor's Guide" by M&T Books, copyrighted1990, incorporated herein by reference. See also the "NetWare® PrintServer" by Novell, March 1991 edition, Novell Part No. 100-000892-001.Briefly, the file server 30 acts as a file manager, receiving, storing,queuing, caching, and transmitting files of data between LAN members.For example, data files created respectively at the PCs 10 and 12 may berouted to the file server 30 which may order those data files and thentransfer the ordered data files to a printer 24 upon command from aprint server in PC 18. The file server 30 may include or may be coupledto a large capacity storage member such as a 10 Gigabyte hard disksubsystem. Furthermore, the printers 32 and 34 may be coupled to thefile server 30 to provide additional printing stations, if desired.

While personal computer equipment is illustrated in FIG. 1, othercomputer equipment may also be included, as appropriate to the networksoftware being executed. For example, Unix workstations may be includedin the network when Unix software is used, and those workstations may beused in conjunction with the illustrated PC's under appropriatecircumstances.

PCs 10 and 12 may each comprise a standard work station PC capable ofgenerating data files, transmitting them onto the LAN, receiving filesfrom the LAN, and displaying and/or processing such files at the workstation. The PCs 10 and 12, however, are not capable of exercisingcontrol over LAN peripherals (unless the network administrator is loggedinto that PC).

A PC capable of exerting limited control over LAN peripherals is PC 22which includes an embedded RPRINTER program. The RPRINTER program is aMS-DOS Terminate and Stay Resident ("TSR") program which runs on a workstation to allow users to share the printer 24 connected to the workstation. RPRINTER is a relatively unintelligent program that does nothave the ability to search printer queues for work. RPRINTER gets itswork from a PSERVER (to be discussed below) that is running elsewhere inthe network. Because they communicate with the attached printer over theprinter's parallel port, RPRINTERs are able to obtain only limitedstatus and to return that status information to the responsible PSERVERover the LAN 6. From a control standpoint, an RPRINTER allows stoppingof a print job and little more. Some printers include RPRINTER featuresby offering internal or external circuit boards that provide the samelimited features of the RPRINTER TSR program running in a personalcomputer.

Another network entity capable of exercising limited control over LANperipherals is a printer 16 with attached circuit board 36 having anembedded QSERVER program. Here, the QSERVER program runs inside an HPLaserJet III® SI printer, and has the capability of searching the fileserver 30 print queues for eligible print files. The QSERVER's searchqueues cannot be dynamically altered nor does the QSERVER respond to anyform of status inquiry. The benefit of the QSERVER is its ability toautonomously search for work. The QSERVER does not require a PSERVERrunning elsewhere in the system to feed it work. Since the QSERVER doesnot have a corresponding PSERVER and it does not itself have any statusand control capabilities, it offers less control than even the RPRINTER.A QSERVER also differs from a PSERVER in that it has extremely limitednotification features and cannot print banners at the beginning of eachprint job.

Another network member having a QSERVER capability is printer 26 whichis coupled to the LAN 6 through an external NetPort device 28.

Other peripheral server programs may be executed to service variousperipherals, such as scanners, copiers, facsimiles etc., and servers mayalso be provided based on network software protocol such as aUnix-compatible Line Printer Remote server ("LPR").

ALAN member capable of exercising significant control over LANperipherals is the PC 18 having a PSERVER program embedded therein.PSERVER has the ability to service multiple user-defined print queues,perform dynamic search queue modification, and provide definednotification procedures for exception (failure) conditions and statusand control capabilities. PSERVER is provided in several forms.PSERVER.EXE is a program that runs dedicated on a work station andcontrols both local and remote printers. The local printers can beconnected to either serial or parallel ports, and the remote printersare printers running elsewhere in the system. Two other forms of thePSERVER program are the PSERVER.VAP and the PSERVER.NLM. These arePSERVER versions that run on the file server 30 itself. The .VAP versionis for NetWare® 286, and the .NLM version is for NetWare® 386. While thePSERVER provides much more capability than the RPRINTER and QSERVER, oneof its drawbacks is that the .EXE version requires a dedicated personalcomputer.

A dedicated personal computer running PSERVER.EXE can control as many as16 local/remote printers and can request print information from manyfile server queues. However, there are several drawbacks to relying onPSERVER to control network printing services. The first drawback is thatmultiple printer streams must all be funnelled through a single networknode and personal computer processor. This can become a bottleneck. Thesecond drawback is that for the most efficient operation, the printersshould be connected to the computer locally, as with the printer 20.This can be an inconvenience for users since it requires the printers tobe clustered around PC 18. The third drawback is that if the controlledprinters are remote as in the case of printer 24 which is serviced byRPRINTER, then the print data must make the trip from the file server 30to the PSERVER PC 18 and then be retransmitted to the printer runningRPRINTER. This is inefficient.

The fourth drawback is the limited amount of printer status and controlinformation offered through PSERVER. It has already been stated thatRPRINTER does not allow for much more than rudimentary status such as"out of paper" and "off line". PSERVER itself for locally and remotelyconnected printers does not offer much more than this because it wasdesigned with consideration of the limitations of the personal computerparallel port. The PSERVER program also allows for its own status andcontrol.

The Network Expansion Board 2 installed in the printer 4 provides manyadvantages and enhanced flexibility over the network peripheral controlentities discussed above. In particular, the NEB-embedded controlleroffers RPRINTER, PSERVER and LPR (Line Printer Remote) functionality(through CRPRINTER, CPSERVER and CLPR programs to be discussed insection 3d below). There is an initialization program named CPINIT (tobe discussed in section 4h below) which allows the networkadministrator's PC 14 complete control over the configuration of NEBfeatures. Due to its embedded nature and the open architecture ofprinter 4, the NEB will have the ability to offer a wide variety ofstatus and control features to the network. That is, verbose amounts ofstatus information may be provided from the printer 4 to the LAN 6, anda great deal of control information may be provided from the LAN 6 tothe printer 4 (for example, exercising printer front panel functionsfrom the PC 14).

To access the extended amount of information available in the NEB, aprogram called CPCONSOL is resident in the network administrator's PC 14and allows the system administrator to view all of the printerinformation which is exported from the printer 4 by the NEB 2. Theprinter information is available even if the RPRINTER functionalconfiguration (CRPRINTER) of the NEB 2 is selected. The PSERVERfunctional configuration (CPSERVER) of the NEB 2 will control theprinter 4 that contains the board. This option will have all of thestandard PSERVER queue search capabilities as well as the notify andstatus features. All of these features can be dynamically controlledfrom a remote work station. The NEB environment and its ability toexport extended status and control information from the printer 4 makesthe combination of the NEB 2 and the printer 4 much more powerful thanthe standard RPRINTER, QSERVER, or PSERVER print methodologies currentlyavailable.

The CPCONSOL program (to be discussed in greater detail in section 4ibelow) provided in the network administrator's PC 14 is capable ofinterfacing with the NEB 2 (and other network members) to perform suchfunctions as displaying current information for a selected networkdevice (interface information, control information, font information,layout information, quality and common environment information, duplexinformation, and miscellaneous information). CPCONSOL is also capable ofsetting or modifying the safe (default) condition of a network device.CPCONSOL may also activate or deactivate applications of the NEB 2 suchas CPSERVER or CRPRINTER (to be discussed below, but generally similarto the PSERVER and RPRINTER software packages discussed above).Furthermore, the CPCONSOL enables the PC 14 to display a log file, clearthe log file, or write the log file to memory such as a local or a filesystem disk. CPCONSOL can also display such printer-related informationon PC 14 as the number of jobs, the number of pages per job, the numberof pages per minute, the time per job, the number of total pages perday, the number of total jobs per day, and the number of days. TheCPCONSOL program is also capable of displaying on the PC 14 suchnetwork-related information as media related and non-media relatedinformation, and of clearing such network statistics.

The CPINIT program (to be discussed in greater detail in section 4hbelow) resident in the network administrator's PC 14 can set upapplication information print services such as CPSERVER and CRPRINTERand configure those applications. CPINIT is also capable of settingand/or displaying device information such as time/date/time zone, buffersize, disk size, logging flag, log limit, and a safe (default)environment flag. CPINIT can also restore default service headings,reset the NEB 2, reboot the NEB 2, command a font download, command anemulation download, display a NEB power-on-self-test ("POST") error,display the NEB 2 firmware level, display the current log file size,etc.

By providing the NEB 2 with PSERVER and RPRINTER capabilities, thepresent invention achieves, with a single circuit board, enhancedfunctionality for the printer 4 with respect to the LAN 6. Therefore,the printer 4 is a true "networked" printer and not just a printerconnected to a network.

While the present invention offers unique advantages on the LAN 6, theseadvantages are also realized when the LAN 6 is coupled to one or moreother LANs in a Wide Area Network ("WAN"). FIG. 2 depicts such a WANwhich includes a first LAN 41 including a server S1 40, PC's 42, 44, and46, and a printer 48. The server S1 40 is coupled to a backbone 50 overa bus 52. The backbone 50 is nothing more than an electrical connectionbetween a plurality of buses. Also connected to the WAN is a second LAN61 comprising server S2 60, PC's 62, 64, and 66, and a printer 68.Server S2 60 is coupled to backbone 50 over bus 54.

The WAN may also include a remote LAN 71 comprising server S3 70, PC's72, 74 and 76 and a printer 78. Since the LAN 71 is remote from theremainder of the system, it is coupled to backbone 50 through a bus 56,a transponder (which may include a modem) 58, and a communication line59.

In such a WAN, assume that PC 42 is a PSERVER requesting the use ofprinter 78. If the printer 78 is equipped with a NEB according to thepresent invention, a direct communication link can be establishedbetween the PC 42 and the printer 78 whereby job information can be sentto printer 78, and status and control information can be sent fromprinter 78 to the LAN 41. Therefore, the NEB according to the presentinvention achieves its enhanced functionality even when installed in aperipheral coupled to a WAN.

FIG. 3 is a block diagram depicting the connection of the NEB 2,according to the present invention, with the printer 4 and the LAN 6.The NEB 2 is directly connected to the LAN 6 via LAN interface 101, andalso to the printer 4 via a bi-directional interface, here a SmallComputer System Interface ("SCSI") 100. The SCSI interface 100 iscoupled to an SCSI bus 102 of the printer 4.

The NEB can also service additional SCSI devices, such as other printers(RPRINTERs) or other peripherals, daisy-chained on the SCSI bus usingstandard SCSI connectivity protocol. Also, the NEB may be used to driveother peripherals across the LAN itself.

The printer 4 is preferably an open-architecture printer including theSCSI bus 102 and SCSI interfaces 104 and 106. Printer 4 also includes aprocessor 108 such as a REDUCED INSTRUCTION SET COMPUTER ("RISC") whichcommunicates with a RAM Memory 110 and with a printing engine 112 whichactually drives the printing mechanism. The RISC processor alsocommunicates with NVRAM 111 for storing information which needs to bemaintained between power cycles, such as user-defined information, andwith ROM 113 from which RISC processor 108 executes printer control. Theprinter 4 may also include a hard disk 114 capable of holding largeamounts of data in a non-volatile way. Printer 4 also has a front paneldisplay 116, and a keyboard 115 for inputting control commands to theprinter.

Preferably, the printer 4 includes an open architecture which takesadvantage of the bi-directional nature of the SCSI interface 100 toprovide a great deal of status (and other) information from the printer4 to the LAN 6 via the NEB, and also to allow fine control of theprinter from a remote location. For example, such open architecture whenused with the bi-directional SCSI interface permits most or all of theinformation on the front panel display 116 of printer 4 to be exportedto a remote location, and also permits most or all of the controlfunctions of the printer front panel keyboard 115 to be activated fromthe remote location.

Briefly, the open-architecture printer 4 comprises four majorsubsystems: Communication; Job Pipe; Page Layout and Raster functions;and Systems Services. The Communication subsystem handles the differentcommunication devices and initiates the start of a job application. Whenthe printer starts to receive data, the Communication subsystem sendsthe first part of the incoming data to each emulator for examination.The first emulator that can process the data becomes the Job Pipedriver. The system then constructs a Job Pipe to process the data (dataflows into one end of the pipe, and page images flow out of the otherend). This Job Pipe comprises many segments one of which is the Job Pipedriver.

The Job Pipe subsystem has a Pipe driver segment (the application for anemulator) and input and output segments. The input and output pipesegments have at least two other segments: for input, source and sourcefilter segments; and for output, an output filter and a data sink. Theinput segment of the Communication subsystem delivers the input datawhich can be supplemented by information from a file system. The Pipedriver processes input and supplemental data. It also generates imagingcommands and page layout information that it sends to the outputsegment. The Pipe driver may store this information to the printer disk(if present). The output segment sends this data to the Page Layout andRaster subsystem.

The Page Layout and Raster subsystem takes the imaging and page layoutinformation and converts it to a raster image for the print engine 112.This section operates completely separately from Job Pipe.

The System Services subsystem provides file system access, consoleaccess, font services, basic system services, and image generationservices. Therefore, a printer 4 having such an open architecture willtake full advantage of the intelligent, interactive NEB 2 to provideincreased functionality to the printer 4 and the entire network.

2. HARDWARE

FIG. 4 is a block diagram of the NEB 2 showing the major componentsthereof. The NEB 2 is coupled to the LAN 6 through network connectors202, 203, and 204. Preferably, the connector 202 is an RJ45 capable ofaccepting a 10Base-T connection. The connector 203 may comprise a DB15connector for accepting a 10Base-5 connection, while the connector 204may be a simple Coax connector capable of accepting a 10Base-2connection. All of the connectors 202, 203, and 204 are coupled to anetwork controller 206 (preferably an Ethernet Network Controller).However, the connector 204 is first coupled through a transceiver 208.

Power is supplied to NEB 2 from a +5V power source in printer 4 throughthe printer expansion port 226. The +5V power is also provided to thepower converters 210 and 212. The power converter 210 provides -9V powerto transceiver 208, while the power converter 212 provides +12V powerfor "flashing" (loading; to be discussed in section 4q below) the EPROM222. Also, the network controller 206 is coupled to an 8 KB static RAM214.

The heart of the NEB 2 is a microprocessor 216, preferably an NEC V53.The microprocessor 216 is coupled to a serial port 218, currently usedfor testing. Also coupled to the microprocessor 216 are a 512 KB dynamicRAM 220, a 256 KB flash EPROM 222, an SCSI controller 224 (correspondingto SCSI interface 100 of FIG. 3) a printer expansion port 226, adiagnostics/failure LED 240, a 256 Byte non-volatile RAM 228, a controlregister 230, and a PROM 232 which stores the Media Access Control("MAC") address which is the unique name for every EtherNet board.

The architecture of the NEB 2 provides an advantage in that it hasunique support features for administration and management of large,multi-area networks. These support features include, for example,printer control and status monitoring from a remote location on thenetwork, (i.e., from the network administrator's office), automaticmanagement of printer configuration after each print job to provide aguaranteed initial environment for the next user, and logs of printerusage statistics accessible across the network for characterizingprinter workload and scheduling toner cartridge replacement. A keyparameter in the NEB design is the ability to access the printer controlstate from the NEB 2 through a bi-directional interface, here the SCSIinterface 100. This allows the printer console information to beexported to the NEB or to an external network node for the programmingof many useful printing support functions.

Table 1 below provides a description of the functions, implementation,and operational notes with respect to the major hardware elements of NEB2.

                  TABLE 1                                                         ______________________________________                                        Function     Implementation                                                                              Notes                                              ______________________________________                                        Network Controller                                                                         National DP 83902                                                                           With DP8392 Coax                                   (206)                      Transceiver                                        Ethernet Interfaces:                                                                       10Base-2 (202)                                                                              Coax connector                                                  10Base-T (204)                                                                              RJ45 connector                                                  10Base-5 (203)                                                                              DB15 connector                                                                (AUI)                                              Embedded Processor                                                                         NEC V53       16-bit/16Mhz MPU                                   (216)                      with DMA, timers,                                                             Interrupts                                         EPROM (Flash)                                                                              256K Bytes    Network program                                    (222)                      code, board BIOS                                                              (Basic Input                                                                  Output Subsystem),                                                            diagnostics                                        NVRAM        256 Bytes     Printer                                            (220)                      Installation                                                                  Configuration on                                                              Network                                            DRAM         512K Bytes    Code execution and                                 (220)                      data buffering for                                                            exp.port                                           SRAM         8K Bytes      Buffering of                                       (214)                      incoming Ethernet                                                             packets                                            SCSI Controller                                                                            NCR 53C90A    30-pin, internal                                   (224)                      I/F configuration                                                             with power                                         MAC Address and                                                                            32 Bytes      Stores MAC                                         Hardware ID PROM           address and Hard-                                  (232)                      ward ID                                                                       information                                        Board Size   100 mm × 125 mm                                                                       Type 2 EXP-I/F                                                                PCB, double-sided                                                             SMT                                                Power        5vdc, 710 ma  DC converter on                                                               board for Ethernet                                                            +12vdc/-9vdc                                       ______________________________________                                    

Preferably, the NEB 2 is installed inside the printer 4 in an expansionor options slot. The NEB 2 is thus an embedded network node with theprocessing and data storage features described above.

The microprocessor 216 implements a data link layer of network packettransmission and reception. Network data transfer overhead is minimizedthrough the use of a dedicated static RAM packet buffer 214 manageddirectly by the network controller 206. The microprocessor 216 accessesblocks of SRAM packet data and network messages through the networkcontroller 206, and moves them into the large DRAM memory 220.

Blocks of print image data and control information are assembled by themicroprocessor 216 for transmission to the printer 4 by the SCSIcontroller 224 using the SCSI transfer protocol of the printer expansionport. Likewise, printer status information is transferred from printer 4back to the NEB 2 in SCSI block format. The SCSI controller 224 operatesconcurrently with the network controller 206 for increased datathroughput for overall NEB performance.

The microprocessor 216 is preferably an NEC V53 chip which is a fast,highly-integrated microprocessor with a 16-bit Intel-compatibleprocessor in support of Direct Memory Access ("DMA"), interrupt, timersand DRAM refresh control. Data bus structure on the NEB 2 is implemented16-bits wide to take advantage of the 8-Bit/16-Bit dynamic bus sizingduring microprocessor I/O transfers. Control firmware and printingapplication software for the microprocessor 216 are stored on the NEB 2in EPROM 222. After power-on self-test, the firmware code is selectivelymoved to the higher-performance DRAM 220 for actual execution. Networkand printer configuration parameters are written into NVRAM 228 when theprinter is first installed onto the network. Thus, NVRAM 228 allows theNEB software to recover the installation parameters after printer powerhas been cycled off and on.

3. SOFTWARE

Software for the LAN comprises a combination of network software, andNEB-customized software such as NEB-embedded software and softwareresident on the network administrator's PC.

3a. Network Software

In the present embodiment, NetWare® network software is used to manageinteractions between nodes of a network such that the client workstations can share and receive services from server nodes such as diskfile servers, database servers, print servers, etc. NetWare® itself is acombination of software modules running on these server nodes and oneach work station node. At least one file server may be provided in aNovell network. NetWare® runs as the operating system for the PC of thefile server to provide basic network core services and utilities. Fileservers can connect to more than one LAN by using up to four networkinterface cards (preferably Ethernet or Token Ring connections). Inthese configurations, "bridging" or "backbone" services are providedbetween a plurality of LANs, as shown in FIG. 2, such that resources,including printers, can be shared "internet" i.e., from one LAN toanother.

On work stations, NetWare® runs in cooperation with the work stationoperating system (DOS or OS/2) as a NetWare® "shell" of controlsoftware. This shell has the effect of extending the services of theworkstation operating system onto the network to make network resourcesappear local to the work station.

Novell PSERVER software has the job of controlling a group of printers(up to sixteen) in order to service printing requests from networknodes. Requests are structured in a form of print queues that are heldon the network file server using network queue management services.Queue entries contain a list of files to be printed. The files containdata to be printed such as tabs, formfeeds, and other PrinterDescription Language ("PDL") commands. Several queues can be serviced bya single PSERVER.

Standard Novell servers are available in different versions depending onthe type of network node they are to execute on. Print server programscan reside on the file server itself. A version of print server softwaremay also be loaded on a stand-alone DOS station node to make that node adedicated print server.

By providing print server functionality (CPSERVER) to NEB 2 of thepresent invention, the NEB and attached printer will offer all theprinting services of a standard Novell print server without the need foran attached PC.

Printers themselves are considered to be either "local" or "remote". Alocal printer is one that is physically connected to the print servernode. In the case of the NEB 2, the local printer is the printer housingthe NEB. A remote printer is managed by RPRINTER programs running in thePCs they are connected to. RPRINTERs receive print data fromPRINTSERVERS running elsewhere on the LAN. The NEB 2 of the presentinvention can be provided with RPRINTER functionality (CRPRINTER) tooffer its printer as a network remote printer. In this mode, it is fullycompatible with standard versions of Novell print servers.

Novell NetWare® provides a number of print utilities to configure andcontrol file server or work station-based print servers and theirattached printers. The Novell program PCONSOLE is a menu-driven utilitythat allows a user (the printer console operator) to create a new printserver, configure up to sixteen local or remote print ports, createprint queues, assign queues to printers, and start/stop printer andserver operations.

3b. NEB-Customized Software

The NEB 2 is bundled with software modules that implement the full rangeof printing services offered by NetWare®. This includes externalNetWare®-compatible modules that execute on work station nodes of thenetwork in addition to internal NetWare®-compatible modules running onthe NEB 2 inside the printer. The specific NetWare®-compatible programsdeveloped for use with the NEB 2 (e.g., the customized CPSERVER andCRPRINTER programs to be discussed below) are provided with the samegeneral operational interfaces as standard printing modules from Novellso as to be familiar to Novell users and network administrationpersonnel. The customized versions include functional extensions thatmake use of the open architecture of the printer 4 to enhance printservice management across the network.

Table 2 shows the functions, implementations, and operational notes forthe customized software developed for the NEB.

                  TABLE 2                                                         ______________________________________                                        Function  Implementation     Notes                                            ______________________________________                                        NEB-specific                                                                            CPSERVER      (92KB)   Customized                                   functions in                     Print Server                                 NEB EPROM CRPRINTER     (40KB)   Customized                                                                    Remote Printer                               NEB-to-Net-                                                                             CPSOCKET      (30KB)   Concurrent                                   work                             multiprotocol                                communication                    operation                                    in NEB                                                                        EPROM                                                                         NEB Environ-            (15KB)   Monitor, load-                               ment in NEB                      er, POST, etc.                               EPROM                                                                         Extensions to                                                                           CPCONSOL.EXE  (180KB)  Remote Control                               NetWare ®                    & Stats, Auto-                               PCONSOLE  CPINIT.EXE    (120KB)  Reconfigura-                                 for Printer                      tion, Print Job                              Control/Con-                     Logs/Statistics                              figuration in                                                                 Administrator's                                                               PC 14                                                                         ______________________________________                                    

3c. NEB-Embedded Software

The software developed for the NEB 2 includes software embedded in theNEB and software loaded into the network administrator's PC 14. TheNEB-embedded software provides both the NetWare®-compatible node andNetWare®-compatible print services directly inside the printer 4 withoutthe overhead of a work station PC and its DOS operating system. TheNEB-embedded software comprises a plurality of application modules(CPSERVER, CRPRINTER, etc.), real-time service modules, network protocolstacks, and a MONITOR program which performs application switching,process extension, device semaphores, and shares buffer-pool management.The functionality of the NEB is determined by the types of applicationmodules and the number of protocol stacks of network layeredcommunication software that are configured into the NEB 2. Interactionbetween the printer 4 and the network is coordinated by the MONITORprogram which responds to real-time events while allocating NEBprocessing time to each application module on a multi-tasking basis.

The NEB software functions at two layers: a "run-time" or real-timelayer; and a "soft-time" or applications layer. The run-time layer iscomprised of components of NEB software that respond to microprocessorinterrupts. This layer services devices such as a timer, queued datatransfer requests from the SCSI port, or LAN data through the protocolstack routine, and the CPSOCKET (to be discussed in section 4j below)communication mechanism.

The soft-time layer is arbited and controlled by the MONITOR program (tobe discussed in section 41 below) which gets control of the NEBmicroprocessor 216 after all real-time events have been serviced. Anon-preemptive (cooperative multi-tasking) approach is used to dividethe processor between the various application modules that are loadedsuch that no one application module can preempt other modules bycapturing the microprocessor.

The NEB EPROM 222 contains up to 256 KB of application module programsand NEB initialization code. At power-up or during a programmed reset,the NEB 2 executes a POST from the EPROM 222 before selectivelytransferring its EPROM code to NEB DRAM 220. If the POST is successful,the NEB 2 will load its protocol stacks and application modules intoDRAM, and begin execution of its application modules.

In its basic configuration, the NEB 2 contains NetWare®-compatibleapplication modules comprising embedded versions of two configurations:the Customized Remote Printer ("CRPRINTER"); and the Customized PrintServer ("CPSERVER"). Preferably, the NEB acts in only one of theseconfigurations at a time. Further, these application modules requirethat a network protocol stack be loaded and functioning within the NEB.

When configured with RPRINTER functionality, the NEB operates itsprinter as a slave to an external print server using a CRPRINTER module.In this configuration, the NEB exports to the LAN only limited printerstatus information in emulation of what the standard Novell print serverexpects from a standard Novell RPRINTER. However, extended statusinformation about the printer will still be available if the CPCONSOLutility (discussed above) is executed in the network administrator's PC14.

As mentioned above, the NEB 2 includes embedded software programsCPSERVER and CRPRINTER which enable the NEB to act with either PSERVERor RPRINTER functionality on the network. The customized NEB-embeddedsoftware which permits peripheral status and control information overthe LAN is CPSOCKET (to be discussed in section 4j below). CPSOCKET runson the NEB and monitors the LAN for communications addressed to both theNEB 2 and the attached printer 4. Further, CPSOCKET communicates withCPINIT and CPCONSOL when they are running. CPSOCKET will maintain atable of default settings for the device environment, download basicconfiguration information (fonts and emulations) at power-up, providedevice information, statistics, and log information for CPCONSOLdisplays, and provide reset, reboot, and download capabilities. CPSOCKETwill also be responsible for the configuration of the NEB 2. Further,CPSOCKET will configure and activate applications on the NEB at therequest of CPINIT. CPSOCKET also insures that the correct protocolstacks are available for each configured application. CPSOCKET willhandle the settings of the NEB 2 and the printer variables at therequest of both CPINIT and CPCONSOL. Finally, the download facility(e.g. the network administrator's PC 14) will contact CPSOCKET to carryout any firmware downloading, such as flashing EPROM 222, that isrequired.

Upon initialization, programs such as CPINIT and CPCONSOL will issue aService Advertising Protocol ("SAP") on the LAN looking for all networkdevices having the customized software of NEB 2. CPSOCKET will receivethis broadcast signal and will respond. CPINIT or CPCONSOL thenestablishes a special connection with CPSOCKET using a customized clientsocket. CPSOCKET will then post multiple listens and will provide clientservice transactions such as NEB control, device information, basicconfiguration information, application information, statistics, andlogging. For example, CPINIT can request that an application beconfigured, and CPCONSOL can request that an already-configuredapplication be activated or deactivated. CPSOCKET will insure that theappropriate option (protocol stack) is available and configured for anapplication before allowing the application itself to be configured.Within the NEB, the CPSOCKET operational module is always activated.

Additional print service applications may be utilized after loadingfurther application modules into the NEB, for example, UNIX printservices and associated protocol implementation.

3d. PC-Resident Customized Software

To further enhance the functionality of the NEB 2, customized softwareis also provided to the network administrator's PC 14. For example, aCustomized PCONSOLE ("CPCONSOL"; to be discussed in greater detail insection 4i below) utility provides extensions to Novell's PCONSOLEprinter utility to enable access to the powerful control and monitoringfeatures of the open-architecture printer 4. For example, the followingare typical status control information available to the network from theprinter through the use of CPCONSOL: (A) status and control informationsuch as online/offline, no response, time/date/time zone, language,offsets, error skip settings, timer, buzzer enable, toner low, paperfull, paper counter, count since last service, paper out, paper jam; (B)font information such as primary, secondary, graphic set, scaling,rotation, elite; (C) layout information such as page orientation, linepitch, character pitch; (D) quality and common environment informationsuch as number of copies, overlay, job complete, command mode, defaultpaper size, current paper size; and (E) configuration information suchas interface, buffer size, feeder select, duplex print, page stackorder, etc.

Furthermore, configuration data for the printer accessible to thenetwork through the use of CPCONSOL includes: (A) network groupinformation such as protocol type, the node name, the file server name,routing, POST error code, NEB firmware level, MAC address, server mode;and (B) printer group information such as safe (default) environment,font, disk present, disk size, initial environment, logging on/off, logfile size, configured/nonconfigured, and net name. Additionally, logscan be kept of print job flow, print engine usage, and network behavior.Examples of such usage and statistical log entries include: (A) networkgroup information such as receive statistics, transmit statistics, andnon-media related information; (B) job entry information such asdate/time/time zone, log-in (user's name), job name, pages, copy count,and print status; (C) initialization entry information; (D) errorcondition entry information; (E) clear log entry information; and (F)printer group information such as the number of jobs, pages/job,pages/minute, time/job, total pages/day, total jobs/day, number of daysand total resets.

CPCONSOL is a menu-driven DOS executable program whose function is toprovide extensions to the Novell PCONSOLE printer utility. The CPCONSOLextension enables access to the additional control and monitoringfeatures of the open-architecture printer 4. These features will enhanceprint service management across the network by allowing the networkadministrator's PC 14 to control and maintain the printer from a remotelocation. In summary, CPCONSOL is the utility that exports printercontrol features to the network administrator, allows reconfiguration ofthe safe (default) environment, and allows the network administrator toview network and printer status, job statistics, and a log of thepreviously-processed jobs and error conditions. CPCONSOL gathers therequested information by communicating with the NEB-embedded softwareprogram module CPSOCKET.

Another customized software program resident on the networkadministrator's PC 14 is Customized Peripheral Initializer ("CPINIT"; tobe discussed in section 4h below) which is also a menu-driven DOSexecutable program. The function of the program is to configure,reconfigure, and initialize the printer 4 attached to the NEB 2.

The CPINIT module will configure the NEB to act as a print server withone attached printer and specifies its primary file server by which theNEB will determine which queues to service. CPINIT is the program thatsupervises all like-customized devices on the LAN (e.g. other NEBsinstalled in other open-architecture printers). CPINIT accomplishes thistask by communicating over the network with other NEBs that residewithin open-architecture peripheral devices. CPINIT is used to configureeach NEB with the appropriate basic configuration information such asconfiguring the NEB as CPSERVER or CRPRINTER. The basic configurationinformation comprises NEB environment settings (including which printserver applications are active), as well as device environment options(e.g. a list of fonts and emulations to download printer initializationtime), and device default settings (such as the internal devicetime/date/time zone, buffer size, disk and logging information, andprinter name). The CPINIT program also displays status information aboutthe NEB (such as the firmware level loaded in the NEB and reports latentPOST errors).

The CPINIT program will broadcast over the network to see which othercustomized devices are available on the LAN. The NEBs attached to suchother customized devices will respond with their identification numbers,their device types, and their configuration states. CPINIT willconstruct a list of these NEBs and devices that will be presented to thenetwrok administrator to allow their configuration or reconfiguration.

A DOWNLOADER program may also be loaded into the network administrator'sPC 14 to download executable files to the NEB across the network (to bediscussed in greater detail in section 4n below).

Another customized program which may run on the network administrator'sPC 14 is CPFLASH which may be used to remotely flash new firmware intoEPROM 222, as will be discussed in greater detail in section 4q below.

4. OPERATION

At first, an overview discussion of the NEB structure and functions willbe provided with respect to the flowchart of FIGS. 5A, 5B and 5C.Thereafter, more detailed descriptions of various aspects of the NEBhardware and software will be provided with respect to sections 4a to4q.

The present invention takes advantage of the bi-directional nature ofthe communication between the printer and the NEB, and the NEB's abilityto process information on a multi-tasking basis. That is, thebi-directional SCSI bus can transmit large quantities of data both toand from the printer, enabling the NEB to receive large quantities ofspecific status data from the printer or even data input from theperipheral (such as image data input from a scanner). The NEBmicroprocessor processes information on a multi-tasking basis(sequential but shared) effectively parallel processing informationreceived from the network and information received from the printer.This multi-tasking processing insures that the NEB is responsive to boththe network and the printer on a near real-time basis.

FIGS. 5A, 5B, and 5C comprise a top-level flowchart depicting a notionalsequence of events which may occur when the NEB and its associatedsoftware is installed in a printer coupled to a local area network.Overall, the printer renders print information and is coupled to the NEBthrough a bi-directional SCSI interface. The printer may also have aparallel port and/or a serial port for receiving print information fromother sources. The NEB is connected to the printer via thebi-directional SCSI interface, the board receiving printer informationfrom the local area network. The board sends print jobs and printerstatus inquiries to the printer over the SCSI interface, receivesprinter status from the printer over the SCSI interface, and reportsprinter status over the network.

Where the NEB is coupled to a data generating device such as a scanner,the board is connected to the scanner through the bi-directional SCSIinterface and is coupled to the network via the LAN interface. The boardreceives status request information from the network and will pass thisinformation to the scanner over the hi-directional interface. The boardwill also receive the data generated by the scanner over thebi-directional interface, and will pass that data onto the network overthe LAN interface.

Illustrating a sequence of events which may occur when the NEB isinstalled in a printer, FIG. 5A begins when power is applied to the NEBat Step S1. At Step S2, the NEB executes a power-on-self-test ("POST")from EPROM 220. At Step S3, if the POST is successfully completed, theprocess moves to Step S5 where the NEB EPROM 222 operational code readsthe network and printer configuration code from NVRAM 228. If the POSTis not successfully accomplished at Step S3, a failure indication islogged at Step S4 and this information may be transmitted to the networkover the LAN interface. An LED failure/diagnostics light on the NEB orprinter may also be activated.

After the network and configuration code have been read from NVRAM 228,the procedure advances to Step S6 where the NEB EPROM operational codereads selected configuration modules, protocol stacks, housekeepingmodules, etc., (e.g., the MONITOR multi-tasking module, CPSOCKET,CPSERVER, etc.) from EPROM 222, and downloads the selected modules toDRAM 220. In Step S6, a configuration is selected (in accordance withthe configuration set by CPINIT) which defines an operational mode (e.g.CPSERVER or CRPRINTER) of the interactive network board. As will bediscussed in greater detail in section 4d below, a binary configurationcode is sent over the LAN and stored in NVRAM 228. After the NEB isbooted up, the configuration code is read from NVRAM using ROM-residentpower-up process steps. Using the ROM-resident process steps,ROM-resident executable modules are selected in accordance with theconfiguration code read from NVRAM. The modules are selected in bit-wisecorrespondence to the binary digits of the configuration code in NVRAM.The selected modules are then stored into DRAM and execution control forthe modules is passed to DRAM whereupon the selected modules areexecuted. In this manner, multiple configurations can be defined andselectively changed.

At Step S7, the EtherNet frame type of the information packetstransmitted on the LAN is determined (as will be discussed in greaterdetail in section 4e below). That is, EtherNet supports four differentframe types: EtherNet 802.3; EtherNet II; EtherNet 802.2; and EtherNetSNAP. To determine the EtherNet frame type, a pre-scan process("PRESCAN") determines what frame type is resident on the LAN (from anyLAN broadcast data), and configures the appropriate NEB-residentprotocol stack for that data. The pre-scan process strips away bytes ofdata from a received LAN packet until the bytes which indicate frametype are reached. Briefly, Step S7 provides the NEB with the capabilityof processing LAN packets of different frame types by: receiving fromthe LAN a frame of data, pre-scanning the frame to determine the frametype, and processing, on the NEB, the identified frame, using anappropriate processing program. The pre-scanning operation includes thesub-steps of stripping a predetermined number of bytes from the head ofthe frame, processing the stripped frame to identify an identificationcode indicative of the frame type, and transmitting the identified frameto the processing program.

At Step S8, a timer module which was downloaded in Step S6 finds thenearest LAN server and requests the current time. After receiving thecurrent time, the process proceeds to Step S9 where it is determinedwhether it is midnight, i.e. whether the returned time indicates a newdate.

Steps S9 through S12 comprise a so-called "autologging" function whichis carried out in the NEB by the CPSOCKET program in order toautomatically and systematically provide status information from theprinter to the LAN (autologging will be discussed in greater detail insection 4k below). In Step S9, if midnight has not been reached theprocedure advances to Step S13. However, once midnight is reached, theNEB microprocessor 216 transmits a request to the printer over the SCSIbus for the printer to return current status to the NEB. For example,the printer may return the cumulative number of pages printed to theNEB. In Step S11, the NEB microprocessor 216 calculates printerstatistics such as pages per job or pages per day, the NEB having kepttrack of the number of jobs sent to the printer and the date. At StepS12, the printer statistics are transferred to a non-volatile memorysuch as the printer's hard disk 114 or NVRAM 111, or the NEB's NVRAM228. Alternatively, Steps S10, S11, S12 may be performed before Step S9,so that statistics are stored every minute.

Summarizing Steps S9 through S12, a method for logging system statisticsof a printer connected via a hi-directional interface to an interactivenetwork board for LAN communication includes the steps of counting inthe printer the number of pages printed, and counting on the board thenumber of jobs printed. The printer is interrogated daily over thebi-directional interface for the number of pages printed, and the boardthen calculates daily statistics using the number of pages, the numberof jobs, and other status information. The daily statistics are thenstored and may be accessed and remotely displayed using CPCONSOL fromthe network administrator's PC 14. An additional feature of the"autologging" function is that different levels of statistics may belogged. For example, at a basic level, only the number of pages for eachjob may be logged. At more advanced levels, the number of pages per jobplus a log of failure conditions may be logged; or the job start and endtimes may be logged in addition to the failure conditions and the numberof pages per job. The logging level is set by CPINIT.

In FIG. 5B, at Step S13, the SAPSERVER program (to be discussed ingreater detail in section 4g below) advertises the NEB as having bothCPSERVER and CPSOCKET identities. Thus, the NEB and attached printer canfunction in its twin roles of PSERVER and customized entity (CPSOCKET;i.e., similar to other LAN peripherals having a NEB installed therein).SAPSERVER is a NEB-resident TSR program that allows more than one serverto advertise network services at the same time on the same node. Thus,CPSOCKET and CPSERVER both advertise their services through SAPSERVERand respond to inquiries from other network applications. Since eachEtherNet board can have only one SAP socket number, SAPSERVER willfunction to advertise both NEB identities without confusion to the LAN.

In summary, Step S13 is a method of identifying a single interactivenetwork board as two network servers (e.g. CPSERVER and CPSOCKET)comprising the steps of transmitting to the network at a predeterminedtime interval a signal indicating that the board is a first type ofnetwork entity, the signal including an identification signal unique tothe board; then, transmitting a second signal to the network at thepredetermined time interval to indicate that the board is a second typeof network entity, the second signal also including the same uniqueidentification signal. Once a signal is received from the networkrequesting that the board perform functions of one of the types ofnetwork entities, direct communication is established between the board(acting as the requested type of network entity) and the network entitywhich generated the request. When the direct communication isestablished, the NEB will utilize a new unique identification signal.

At Step S14, both the LAN and the SCSI interfaces are checked for datathat is being directed to CPSOCKET (to be discussed in greater detail insection 4j below). The SCSI interface will typically have printer statusdata which is to be passed to the LAN in response to apreviously-received request for status. CPSOCKET is the NEB-residentresident TSR program that responds to such requests for connection,requests for data download, or requests for services from remoteutilities. CPSOCKET gathers information from the NEB or the printer, asneeded, monitors requests to write to the log file, monitors applicationrequests for device status, and maintains job statistics, as discussedabove.

Briefly, the CPSOCKET program is a method of interfacing an interactivenetwork board between the network and a peripheral device, comprisingthe steps of transferring a program from board ROM to board RAM forexecution from the RAM; and monitoring, with the program, a boardnetwork interface to detect a network communication directed to theperipheral device. The program then commands the peripheral device toperform a function in response to the network communication, andmonitors a board bi-directional peripheral interface to detect and storestatus information of the peripheral device. Finally, the programoutputs the peripheral device status information onto the networkthrough the network interface in response to another networkcommunication.

In FIG. 5B, Steps S15 and S17 indicate "run-time" layer functions, andStep S20 represents a "soft-time" application layer. First, Step S15determines whether data is being received over the LAN. When LAN data isreceived, the process proceeds to Step S16 and the software protocoltype is determined (to be discussed in greater detail in section 4fbelow). For example, the Ethernet data received over the LAN may be oneof the following software protocols: e.g. NetWare® over SPX/IPX; UNIXover TCP/IP; or Mac Systems 7 over AppleTalk. Basically, the softwareprotocol type may be determined according to the frame packet typesensed in Step S7 above.

If CPSOCKET determines that LAN data is not being received in Step S15,Step S17 determines whether SCSI data is being received, and if SCSIdata is being received, it is input from the printer in Step S18, andthen stored in DRAM 220 in Step S19.

After the storing of printer data in Step S19, or if SCSI data is notbeing received in Step S17, the process proceeds to Step S20 where"soft-time" tasks are performed on a multi-tasking basis as controlledby a multi-tasking software program called "MONITOR" (to be discussed ingreater detail in section 41 below). Step S20 is therefore a"background" process which runs concurrently throughout the flowchartdepicted in FIGS. 5A, 5B and 5C. That is, whenever "soft-time" tasks arebeing performed, the microprocessor 216 will ensure time-shared,parallel, non-preemptive processing of the "soft-time" tasks.

More particularly, MONITOR is a software module downloaded from EPROM222 to DRAM 220 in Step S6. MONITOR is a non-preemptive multi-taskingmonitor which distributes the processor usage among the severalapplication tasks which are currently active. The non-preemptive natureof the monitor requires that each application task periodicallyrelinquish control so that other tasks gain the opportunity to execute.The relinquish control mechanism is implemented using a softwareinterrupt to pass control to the MONITOR. At an interrupt, MONITOR savesthe state of the current task, restores the state of another activetask, and resumes (or commences) execution of the new task. The taskwhich originally relinquished control eventually regains control at theinterrupt point, i.e. with its context restored to the same condition aswhen it relinquished control.

In summary, Step S20 comprises the step of monitoring a plurality ofapplication tasks in a multi-tasking interactive network board todistribute processor resources. A memory stores a first application taskwhich may queue a file server to get a network interface to obtain aqueue of print files to be printed, and which channels the print filesto a printer coupled to the board through an interface. The memory alsostores a second application task which may receive remote statusinquiries over a LAN interface, interrogate the printer over abi-directional interface to obtain printer status and a response to thereceived status inquiry, and provide the status information over the LANinterface to the status requester. The first and second applicationtasks each include a relinquish command which causes the currentlyexecuting application task to periodically relinquish control to theMONITOR. The MONITOR saves the state of the relinquishing task, restoresthe state of the non-relinquishing task, and resumes execution of thenon-relinquishing task.

In FIG. 5C, presuming that data has been received over the LAN at StepS15, Step S21 determines whether the received data is for a print job ornot. If it is for a print job, microprocessor 216 acts as the LAN fileserver for an active print file and transfers print job blocks to DRAM220 at Step S22.

At Step S23, microprocessor 216 assembles blocks of image data andcontrol information, and sends the blocks to the printer through theSCSI interface. In this step, the microprocessor 216 effectively adds"beginning of job" and "end of job" indications to the data streamreceived over the LAN. It does this by opening the XP (data) channel atthe beginning of a print job, and by closing the XP channel at the endof a print job.

At Step S24, the process waits until the print job is complete. Once theprint job is complete, Step S25 will unambiguously set the printer to adefault environment. It is also possible to set the defaultconfiguration before (or during) the print job. That is, the NEB itselfwill ensure that the attached printer is set to a default environmentwhich specifies, for example, default fonts, papers trays, collation,stapling, etc., to insure that the next print job will be started withthe printer in a known configuration (to be discussed in greater detailin section 4m below).

Step S25 may be thought of as guaranteeing a safe environment for theprinter by ensuring that the printer settings (e.g. portrait mode,duplex, etc.) are returned to between logical printing jobs. Forexample, while Novell NetWare® includes the ability to prefix every jobwith printer escape sequences to reset the printer environment, suchescape sequences reside in a database on the network file server, andthe print job in question might not originate from that file server. Inorder to ensure a guaranteed safe environment, the NEB will store therequisite configuration parameters, and will be responsible forresetting the printer environment between print jobs.

In summary, a method for providing a default configuration to a LANprinter having an interactive network board coupled thereto includes thestep of receiving a default configuration over a LAN interface at theinteractive network board. The default configuration may be stored inNVRAM 228 in the NEB or stored in an NVRAM or disk in the printer overthe bi-directional interface between the board and the printer. Then,the default configuration is downloaded from the NVRAM in the printer tothe DRAM 220 on the board over the bi-directional interface. When theboard receives print information over the LAN interface and provides theprint information to the printer over the bi-directional interface, theboard detects an end of print job. In response to this detection, thedefault configuration is sent to the printer whereby the printer is setin its default configuration.

Additionally, a plurality of default configurations may be stored, andan appropriate default configuration may be selected remotely fromanother LAN entity. For example, a method of setting one of a pluralityof default configurations may include a step of detecting, at the board,the origination of a print job and identifying the source of the job.Subsequently, an appropriate default configuration is selected fromamong the stored configurations, and the selected default configurationis then sent to the printer at the beginning or end of the print job.

In FIG. 5C, if it is determined that a print job is not required at StepS21, Step S26 determines whether a status request has been made over theLAN requesting the status of the attached printer. If it is determinedthat a status request has been received, Step S27 determines the type ofstatus request. For example, printer status such as error codes, thenumber of pages printed, the toner status, etc., may be requested.

At Step S28, the microprocessor 216 retrieves the requested status datafrom DRAM 220, assembles the status data, and sends it to the LANthrough the LAN interface (to be discussed in greater detail in section4i below). Thus, in Step S28, more than simple "on/off" information maybe transmitted to the LAN so as to inform the LAN of the detailed statusof the printer. In a broad application, Step S28 encompasses the exportof printer front panel status over the LAN, and the import of frontpanel control commands from the LAN. That is, the network administratorat the PC 14 may request and receive a display indicating all of theprinter information included on the printer front panel display 116. Thenetwork administrator may then activate different printer front panelfunctions on his/her PC, and such functions will be transmitted to theprinter where the selected control will be effected.

In summary, at Step S28, a method for remotely controlling amanually-operable function of a networked printer through an interactivenetwork board having a LAN interface for LAN communication, comprisesthe step of issuing, at a remote location, a command to the board thatwill cause the board to transfer printer status information through theboard to the remote location through the LAN interface. At the remotelocation, a printer status may be displayed, and a second command may beissued at the remote location to the board through the LAN interface tocause the board to perform a manually-operable function.

If the received LAN data is neither a print job nor a status request, itis determined at Step S29 that the received data may be a downloadoperation, i.e., a transfer of data into the NEB for updating the ROM orRAM applications, e.g. download may be utilized for transientdiagnostics to be run on the NEB.

First, at Step S30, the data is downloaded from the LAN to the DRAM 220(to be discussed in greater detail in section 4n below). That is, thedownload is a process by which data may be loaded into a network nodeand then acted upon or executed. For example, anything from patch code,to manufacturing test routines, to firmware updates for the EPROM may bedownloaded. Also, application modules may be stored in the LAN fileserver and then downloaded to the NEB every morning.

In summary, the downloading of data from LAN to DRAM comprises a methodfor altering an operational mode of an interactive network board havinga LAN interface, including the step of activating a LAN communicationprogram for execution from DRAM, the communication program channellingprint information on the LAN to a peripheral printer. Executableinstructions which correspond to the altered operational mode are thendownloaded into DRAM via the LAN interface. The board is then commandedvia the LAN interface to begin execution of the altered operationalmode.

At Step S31, it is determined whether the downloaded information isdestined for EPROM 222 or DRAM 220. If the information is destined forEPROM, a ROM image is assembled at Step S32 (to be discussed in greaterdetail in section 4o below). For example, downloading of EPROM firmwarefrom a remote location provides unique flexibility. In particular,downloading of on-board test routines, and changing EPROM configurationfirmware can be performed from a remote location after the board isinstalled in the printer.

Step S32 is the process which constructs the binary image file which isto be programmed into the EPROM 222. The data destined for the EPROM isfirst downloaded to DRAM 220 where a utility reads a configuration filecontaining the names of the modules to be placed in the ROM image. Then,a complete binary image file is constructed containing all of thespecified modules. A header precedes each module in the image, theheader identifying the module, describing its attributes, and pointingto the succeeding header to aid in locating the modules during loading.The last module loaded in the EPROM is the EPROM-resident code. It isplaced at the end of the ROM image so that the power-up initializationcode resides at the address expected by the microprocessor 216.

In summary, Step S32 comprises a process for formatting a binary imagefile which contains executable code modules for storage in the EPROM.First, a configuration file is read which specifies the code moduleswhich form the binary image. Next, a header is formed for each modulespecified in the configuration file, the header including anidentification of the module, a definition of the module's attributes,and a pointer to a header for a succeeding module. The binary image fileis then constructed containing the specified modules and theirassociated headers. Finally, a module of ROM-resident code is appendedto the binary image, the ROM-resident code receiving control atpower-up, providing POST, loading at least some of the modules from thebinary image file into DRAM 220, and providing basic board I/O services.

Before writing new data into EPROM 222, it is first necessary tounequivocally ensure that a write operation is, in fact, intended.Obviously, any accidental writings into EPROM 222 could render the NEBunusable. Therefore, before information may De "flashed" to EPROM 222, aspecified sequence of events will occur in Step S33 in order to accessthe EPROM (to be discussed in greater detail in section 4p below). Inthe present embodiment, unless two data bits are changed in two separateI/O locations, the +12 Volts necessary to write to the EPROM will not beprovided.

Briefly, a method of ensuring that the EPROM is not accidentally writteninto comprises a method of performing a flash operation on an EPROMresident on an interactive network board having a processing unit and amemory, including the step of sending an I/O write signal to theprocessing unit. Then, the processing unit generates a first address inthe memory to cause a first bit to be in a predetermined state inresponse to the I/O signal. A power unit is then caused to provide +12Volts to a transistor in response to the first bit being placed in thepredetermined state. Then, an I/O receive signal is sent to theprocessing unit which generates a second address in the memory to causea second bit to be in a preselected state in response to the I/O receivesignal. Then, the transistor is turned on in response to the second bitbeing placed in the preselected state causing the +12 Volts to flow to apower terminal of the EPROM, allowing a write operation to take place.

Before the new ROM image is actually stored in EPROM 222, at Step S34the new ROM image must be checksummed and verified with a checksum valuesent after the ROM image is received. Prior to erasing EPROM 222, dataand modules to be preserved, such as the MAC address, must be loadedinto DRAM 220 within the new ROM image.

After determining that the ROM image is verified and after preservingall required data into the new ROM image stored in DRAM 220, it isnecessary to clear and erase EPROM 222 to ensure no corruption of dataupon loading of the new ROM image. Accordingly, at Step S35, EPROM 222may be erased a plurality of times before the new ROM image is storedtherein.

After erasing EPROM 222 at Step S35, the new ROM image is "flashed" intoEPROM 222 in Step S36 (to be discussed in greater detail in section 4qbelow).

In summary, Step S36 relates to a method for remotely alteringprogrammable firmware on an interactive network board having a LANinterface including the step of activating a LAN communication programfor execution from DRAM on the board, the communication programchannelling print information on the LAN to a peripheral printer. A ROMfirmware image is then downloaded to the DRAM on the board via the LANinterface. It is next confirmed that the ROM image has been downloadedto the target board, and the integrity of the ROM image is confirmed.The board is then commanded to electronically erase the EPROM, and thenthe EPROM is flashed with the new ROM image. Additionally, a "flashcomplete" signal may be sent to the LAN after the flash operation, ifdesired.

After the information is flashed to the EPROM 222, the NEB is thenre-booted from the new ROM firmware image in EPROM 222 at Step S37, andthe process returns to Step S1.

In FIG. 5C, if Step S31 determines that RAM information is beingdownloaded, such information is first assembled in DRAM 220 via StepS38. Subsequently, Step S39 executes the RAM program, and the processreturns to Step S13 wherein SAPSERVER advertises PSERVER and CPSOCKETentities.

This discussion concludes the overview of the NEB structures andfunctions when the NEB is installed in LAN-networked printer. A moredetailed description of the operation of various aspects of the NEBhardware and software will now be provided.

4a. Power-on Sequence

Immediately following power-on, NEB 2 executes a power-on self test(POST), following which the NEB loads operational software from EPROM222 into DRAM 220 for execution.

More specifically, immediately following power-on, microprocessor 216accesses POST program modules located in EPROM 222. Microprocessor 216executes POST directly from EPROM 222 to test the functionality of themicroprocessor, integrity of the programs stored in EPROM 222 (forexample, via checksum verification), operability of DRAM 220 (forexample, through read/write cycles), operability of SCSI controller 224,data integrity of NVRAM 228, and operation of control register 230. POSTmay also include a comparison of the MAC address stored in PROM 232 witha MAC address downloaded into EPROM 222.

POST further includes operational checks of network-related hardware.More specifically, POST may include operability checks for SRAM 214 (forexample, through read/write cycles), as well as a check of networkactivity to verify operation of network controller 206.

Operation of other hardware in NEB 2 may be determined directly throughadditional POST testing. In some cases, where it is not possible formicroprocessor 216 to test operation of hardware directly, as in thecase of connectors 202, 203 and 204, proper operation of that hardwaremay be implied through result codes received from direct testing.

Upon termination of POST, microprocessor 216 puts a checksum code ontoserial port 218 and then enters a window of quiescent operation (forexample, a one second window) during which microprocessor 216 canreceive commands (e.g. for testing--see paragraph 5 below) via serialport 218. The POST checksum code may be obtained by a device coupled toserial port 218 to determine the outcome of POST. For example, a noerror condition may be indicated by a POST checksum code of "0000h",while a POST checksum code indicating an error may be indicated by anon-zero hexadecimal value which indicates the area of failure. In thecase of failure, microprocessor 216 may also illuminate LED 240 on NEB 2to signal to a user that an error has been detected. Preferably, LED 240is illuminated on power-up and is only turned off if POST is successful.

Following successful completion of POST and in the event that nocommands are received via serial port 218 during the one secondquiescent window of activity, microprocessor 216 begins to load softwaremodules stored in EPROM 222 into DRAM 220. Microprocessor 216 does notexecute those software modules directly from EPROM 222, but rather loadsthose modules into DRAM 220 for execution from DRAM 220. By virtue ofthis arrangement, it is possible to select the specific modules that areretrieved from EPROM 222 for execution out of DRAM 220 so as to permitflexible configuration of NEB 2 (see section 4d below). For example, inaccordance with a configuration command stored in NVRAM 228,microprocessor 216 may retrieve selective modules from EPROM 222 forloading into DRAM 220 and for execution from the DRAM.

FIG. 6 shows the sequence by which different modules are retrieved fromEPROM 222 and loaded into DRAM 220. In Step S6001, microprocessor 216loads the SCSI driver from EPROM 222 into DRAM 220. The SCSI driverprovides for operational sequence and control over SCSI controller 224and permits interface with printer 4 so as to send printer 4 print dataand so as to send and receive control information to and from printer 4.

In Step S6002, microprocessor 216 loads the link support layer, or"LSL", from EPROM 222 into DRAM 220, and in Step S6003 microprocessor216 loads network driver software from EPROM 222 into DRAM 220, andthereupon microprocessor 216 begins to execute the link support layerand the network driver from DRAM 220. The link support layer and thenetwork driver provide common access to LAN communications on LAN bus 6.More particularly, as shown in FIG. 7, all networked devices, includinga device such as NEB 2, interface with LAN bus 6 via an electricalinterface 301 such as the network controller 206 used on NEB 2. Theelectrical interface 301 is driven by network driver 302 which in turnreceives LAN frame data from link support layer software 304. Both thelink support layer 304 and the network driver 302 are common todifferent kinds of network software. For example, as further shown inFIG. 7, network application programs, such as those provided in NetWare®software by Novell (as illustrated at Arrow A) interface with the linksupport layer and the network driver via an internetwork packet exchangeprogram, or "IPX", 305 and a sequenced packet exchange program, or"SPX", 306. On the other hand, network application programs from UNIXprovided by AT&T (as illustrated at Arrow B) interface to the LSLthrough "IP" module 315 and "TCP" module 316.

In NEB 2, only one type of network application programs is normallyexecuted at any one time (although multiprotocol operations are possibleas discussed in section 4f below). Explanation here will be made forNetWare® network application programs although it is also possible forUNIX network application programs to be executed as well.

In Step S6004, microprocessor 216 loads a PRESCAN program from EPROM 222and stores it into DRAM 220, and thereupon begins executing the PRESCANprogram from DRAM 220. PRESCAN software interfaces with the link supportlayer to determine the frame packet type being transmitted on LAN bus 6.More particularly, as described above, there are four different possibleframe packet types on an Ethernet-type network LAN bus: Ethernet 802.3,Ethernet II, Ethernet 802.2, and Ethernet SNAP. As described more fullybelow in section 4e, the PRESCAN software module monitors networkcommunications on LAN bus 6 to determine the frame packet type. Theframe packet type, once determined by PRESCAN, is stored in apredetermined common location in DRAM 220 for use by other networkcommunication modules in the NEB. After determining the frame packettype, PRESCAN signals microprocessor 216 that its tasks are completedand allows microprocessor 216 to overwrite the memory occupied by thePRESCAN program with another program module.

In Step S6005 microprocessor 216 retrieves the IPX and SPX programmodules from EPROM 222 and stores them in DRAM 220, and thereupon beginsexecuting the IPX and SPX modules from DRAM 220. Both IPX and SPX usethe frame packet type determined by the PRESCAN module.

In Step S6006 microprocessor 216 retrieves the CNETX program module fromEPROM 222 and loads that module into DRAM 220 and thereupon beginsexecution from DRAM 220. CNETX provides localized DOS-like functionalityto the NEB.

In Step S6007, microprocessor 216 loads the SAPSERVER program modulefrom EPROM 222 into DRAM 220 and begins executing the SAPSERVER modulefrom DRAM 220. As described more fully below in section 4g, SAPSERVER isa program module which allows two network server entities, such asCPSOCKET and CPSERVER, to advertise simultaneously from the singlenetwork node assigned to the NEB board, even though conventional networkapplication programs such as those provided by NetWare® only permitadvertising of a single network server entity from each network node.

In Step S6008 microprocessor 216 retrieves the non-preemptivemulti-tasking MONITOR (see section 41 below) from EPROM 222 and storesit into DRAM 220 and begins executing the multi-tasking monitor fromDRAM 220.

In Step S6009 microprocessor 216 retrieves the CPSOCKET server softwaremodule from EPROM 222 and loads it into DRAM 220 and begins executingthe CPSOCKET server from DRAM 220. As will be described more fully belowin section 4j, CPSOCKET initiates a request to SAPSERVER to advertise onbehalf of CPSOCKET, and SAPSERVER begins making SAP advertisements onLAN bus 6.

In Step S6010 microprocessor 216 retrieves print application serverssuch as CPSERVER or CRPRINTER from EPROM 222 and loads the printapplication servers into DRAM 222. In the case of CPSERVER,microprocessor 216 begins executing the loaded print application serversfrom DRAM 220 which in turn requests SAPSERVER to make SAPadvertisements on behalf of the print server. As described more fullybelow in section 4g, SAPSERVER interleaves advertisements for theCPSOCKET server and for the print server thereby acting as a surrogateSAP entity for both the CPSOCKET server and the print server.

4b. Interfacing A Peripheral With A Local Area Network

According to the broad aspects of the present invention, a peripheralsuch as a printer is coupled to a LAN using an interactive network boardhaving software programs embedded therein. Preferably, the connectionbetween the printer and the NEB is an SCSI interface so that largeamounts of print data and status data are carried bi-directionallybetween the NEB and the printer. EPROM 222 stores a plurality ofsoftware modules for operationally configuring the NEB in the PSERVER orRPRINTER or LPR functional configurations. The EPROM 222 also stores anumber of status control software modules for exporting statusinformation from the printer over the LAN, and for importing controlinformation from the LAN to the printer. The EPROM-resident firmware isdownloaded to the DRAM 220 upon power-up (as discussed in section 4aabove), whereby the MONITOR multi-tasking program executes soft-timetasks until run-time interrupts are received from either the LAN or SCSIinterfaces.

NVRAM 228 stores a configuration word which specifies which modulesstored in EPROM 222 should be downloaded into DRAM 220 in order toconfigure the NEB with either a PSERVER or RPRINTER functionality. Themicroprocessor 216 executes the programs from DRAM 220, allowing printjobs to be received from the LAN and sent to the printer for printing,and allowing printer status to be returned over the LAN in response to astatus request.

The particular details of the structure and functions for interfacingthe peripheral to the local area network are set forth above withreference to FIGS. 4, 5A, 5B and 5C, and in the following sections.

4c. The Bi-Directional Interface Between The Local Area Network And ThePrinter

The provision of a bi-directional SCSI interface between the NEB 2 andthe printer permits a large amount of status information to be extractedfrom the printer, while still providing the print data to the printer.Further, by utilizing the bi-directional SCSI interface, the printer canrespond to control commands issued from a remote location over the LAN.For example, the network administrator may issue a control command fromhis/her PC 14 that requests a particular print job be printed aplurality of times, with high image density, and then stapled. Suchcontrol commands are sent to the NEB 2 over the LAN 6, and the NEB 2transmits these control commands to the printer through the SCSI bus102. At the same time, the actual print data is transferred from fileserver 30 to the NEB 2, where the print data is packaged in blocks andtransferred to the printer over the SCSI bus 102. Preferably, the NEB 2indicates the "start of print job" by opening the XP data channel to theprinter. Likewise, the NEB 2 indicates "end of print job" by closing theXP data channel to the printer. Therefore, the NEB 2 can provide suchindications to the printer.

The use of the bi-directional SCSI interface on the NEB 2 also permitsother types of peripherals to be coupled to the LAN. For example, sincethe SCSI interface is capable of transmitting large quantities of datato the LAN from the peripheral, it is possible to couple the NEB to animage data generating device such as a scanner (e.g., where printer 4 isan Optical Character Recognition ("OCR") device) or a facsimile machine.Thus, data produced by the image generating device may be transferred tothe NEB over the SCSI interface, and then put on the LAN for storage orretrieval by any of the LAN entities. As with a printer, largequantities of detailed control/status information can also be providedto/from the image data generating device.

The detailed structural and functional features of the bi-directionalSCSI interface on the NEB are set forth above with reference to FIGS. 4,5A, 5B and 5C, and in the following sections.

4d. ROM Firmware Configuration

As described earlier with respect to FIG. 5A, Step S6 downloads selectedsoftware programs from EPROM 222 to the DRAM 220 for execution (see alsoFIG. 6 and section 4a). The EPROM 222 is delivered with firmware moduleswhich permit the NEB 2 to be configured with either RPRINTER or PSERVERfunctionality. Therefore, the functionality of the NEB 2 will bedetermined by which of the stored programs are downloaded from EPROM 222to DRAM 220 in accordance with the configruation code stored in NVRAM228.

The NEB 2 firmware is configured initially, and can be reconfiguredsubsequently by running CPINIT on the network administrator's PC 14 (seesection 4h below). However, even in an unconfigured state, NEB 2 itselfwill always activate those software modules needed to perform basiccommunication with the LAN. Using CPINIT, the network manager candetermine, remotely, the current configuration of the NEB, or he/she canchange the configuration as desired. Since the configuration informationis stored in EPROM on the NEB board, the configuration information isretained across power cycles.

The process by which the software programs for a particularconfiguration are downloaded from the EPROM 222 to the DRAM 220 will bedescribed below with respect to FIG. 8.

After the board has been powered up at Step S1, the process proceeds toStep S8001 where microprocessor 216 accesses EPROM-resident code in theEPROM 222 to read a configuration code (typically a word) from NVRAM228. The configuration code will specify modules which can provide theNEB with either a PSERVER or RPRINTER functionality. Although thepresent embodiment includes only RPRINTER or PSERVER functionalconfigurations, other configurations may be utilized where, forinstance, the NEB 2 is installed in a different LAN entity, such as ascanner or a facsimile machine.

After reading the configuration code from NVRAM 228, the microprocessor,at Step S8002, forms a configuration mask whose bit pattern correspondsto the read configuration code. At Step S8003, a loader module residentin EPROM 222 compares the configuration mask to the plurality offirmware modules stored in the EPROM 222.

In detail, in Step S8004, a process begins whereby the EPROM-residentsoftware modules are selected in bit-wise correspondence to the binarydigits of the configuration code read from NVRAM 228. If it isdetermined in Step S8004 that the currently-examined bit of the bitpattern matches a stored module, then that module is selected (at StepS8005) for downloading to DRAM 220, and the process skips to the nextbit at Step S8006. Likewise, if Step S8004 determines that a bit of thebit pattern does not match the stored module, the process skips to thenext bit at Step S8006.

At Step S8007, it is determined whether the bit tested in Step S8004 isthe last bit of the configuration mask bit pattern. If the tested bit isnot the last bit, the process loops back to Step S8004, where the nextbit of the bit pattern is tested with respect to the next stored module.When the last bit of the configuration mask bit pattern has been tested,the selected software modules are downloaded from EPROM 222 to DRAM 220at Step S8008.

In the present embodiment, the software modules are loaded in thefollowing sequence: SCSI Driver; Link Support Layer; Network Driver;Prescan; IPX/SPX; CNETX; SAPSERVER; MONITOR; CPSOCKET; and PrintApplications (e.g CPSERVER, CRPRINTER) (see FIG. 6).

After all of the software modules which correspond to the configurationcodes stored in NVRAM 228 have been downloaded to DRAM 220, the loaderfunction will pass program execution control to the MONITORmulti-tasking program at Step S8009.

As discussed earlier, the configuration code stored in NVRAM 228 may beremotely altered using CPINIT. This provides greater flexibility formaking minor modifications to CPSERVER or CRPRINTER, or where entirelynew configurations are desired to be set. Therefore, at Step S8010, anew configuration is received over LAN 6, and is loaded into NVRAM 228at Step S8011. Preferably, the old configuration code will be erased oroverwritten with the new configuration code. Then, the NEB rebootsitself and returns to Step S1.

4e. Determining Frame Packet Type Using PRESCAN

On any local area network, data is transmitted between network devicesin packets or frames. But even in the context of a common networkarchitecture, such as Ethernet, more than one format for the frame maybe supported. Thus, even though it is known that Ethernet architectureis being used, it is not possible to determine the arrangement of datawithin each physical frame or packet of information on the Ethernet bus.In particular, as described above, Ethernet supports four arrangementsof data, or formats, as follows: Ethernet 802.3, Ethernet II, Ethernet802.2, and Ethernet SNAP.

In conventional network devices-, which provide for a manuallyselectable operator interface, it is possible to advise the networkdevice of the particular frame type being used on the Ethernet network.In the context of NEB 2, for which operator access is provided only viathe network interface (or via the serial port 218 in a testconfiguration), it is not possible to set the frame packet type withoutfirst allowing operator access to the local area network which, ofcourse, requires knowledge of the frame packet type.

The PRESCAN software module allows NEB 2 to automatically determine theframe packet type currently being used for LAN communication on the LANbus by monitoring broadcast communications on the LAN bus until theproper frame packet type is recognized. PRESCAN makes this determinationbased on recognizable components that are common to all four framepacket types used on Ethernet.

In more detail, FIG. 9 shows the physical construction of differentframe packets used on Ethernet. As shown in FIG. 9, a physical frame 411being transmitted on the LAN bus includes a 6-byte section 412 forstoring the destination MAC address, and a 6-byte section 413 forstoring the source MAC address. These 12 bytes comprise the first 12bytes of LAN data packets regardless of the frame type being used forLAN communication. A data section 414 follows these 12 bytes. The datasection is comprised of a variable number of bytes which are not usedfor the same purposes by the different frame packet types and which donot have the same number of bytes for the different frame packet types.

Following the indeterminate area 414, the LAN communication packetincludes an IPX header 415 the first two bytes of which always has thevalue "FFFF" (hexadecimal). The remainder of the packet 416 follows theIPX header and comprises the data and other commands which characterizeeach different type of LAN communication packet.

PRESCAN operates by monitoring the LAN communication in accordance witheach of the different packet types until the common area (such as IPXheader 415) is recognized in one of those packet types. PRESCAN thenstores that packet type for use by other network communication programs.

FIG. 10 is a detailed flowchart for showing operation of the PRESCANmodule. In Step S1001, microprocessor 216 retrieves the PRESCAN modulefrom EPROM 222 and loads it into DRAM 220 and thereupon begins executionof the PRESCAN module. The PRESCAN module is executed before the SPX andIPX modules, even if microprocessor 216 retrieves those latter modulesfrom EPROM 222 and loads them into DRAM 220 before the operationalsequence shown in FIG. 10 is complete. More particularly, properoperation of the SPX and IPX program modules depends upon theidentification of the frame packet type by PRESCAN and thereforeexecution of SPX and IPX is deferred until after PRESCAN determines theproper frame packet type.

In Step S1002, PRESCAN simultaneously binds through LSL to all fourframe packet types, namely, Ethernet 802.3, Ethernet II, Ethernet 802.2,and Ethernet SNAP. That is, PRESCAN configures LSL such that for eachpacket of LAN communication, LSL provides a data group corresponding toeach of the four frame packet types. Thereafter, PRESCAN goes inactivepending reactivation by an interrupt from the network driver.

In Step S1003, the network driver monitors communications on the LAN busfor broadcast traffic. Broadcast traffic means that the destination MACaddress 412 is unspecified or is given a global specification of"FFFFFFFFFFFF" (hexadecimal). The network driver continues to monitorcommunications on the LAN bus for broadcast traffic (Step S1004) untilbroadcast traffic is received, whereupon flow advances to Step S1005. InStep S1005, the MAC address fields 412 and 413 are stripped off thereceived data packet and the remainder of the data packet is provided toLSL. In Step S1006, LSL interprets the frame packet in accordance witheach of the frame packet types and provides a data group incorrespondence to each of the frame packet types. In Step S1007, thenetwork driver reactivates PRESCAN which determines which data groupprovided by LSL has the proper first two bytes, of an IPX header, namely"FFFF" (hexadecimal). That is, because of the variable data area 414(variable data area 414 corresponding to each of the different packettypes (FIG. 9)), LSL will properly identify the IPX header 415 inaccordance with only one of the frame packet types. In Step S1007,PRESCAN searches for the IPX header and, in accordance with which of thefour data groups is provided by LSL, it is able to determine a framepacket type that is currently being used on the LAN bus.

In Step S1008 PRESCAN stores the corresponding frame packet type in acommon area in DRAM 220 so that the frame packet type can be used byother network application programs such as SPX and IPX. Thereafter, inStep S1009, PRESCAN frees its storage area in DRAM 220 so thatmicroprocessor 216 may overwrite that data area with other softwaremodules, if desired.

4f. Multiprotocol Operation

In a multiprotocol operation, two different operating systems carry onLAN communications over a single local area network bus, but usingrespectively different operating protocols. For example, aNovell-compatible operating system communicates over a LAN bus usingSPX/IPX operating protocol, while a UNIX-compatible operating systemcommunicates over the LAN bus using a TCP/IP operating protocol. Otheroperating systems, such as the AppleTalk® operating system provided byApple Corporation, use respectively different operating protocols forLAN communication over a single network bus in a multiprotocol networkenvironment.

Ordinarily, NEB 2 is configured to communicate to a single networkoperating system, but it may also be configured to operate in amultiprotocol network environment, for example, a combined Novell/UNIXmultiprotocol environment. In this configuration, NEB 2 includes aNovell-compatible peripheral server, such as the aforementionedCPSERVER, which checks job queues in a file server on a Novell operatingsystem, as well as a UNIX-compatible peripheral server, such as theaforementioned CLPR (Custom Line Printer Remote), which, in coordinationwith checks made by CPSERVER, also checks for job queues in a fileserver for a UNIX operating system. Both servers, here CPSERVER andCLPR, service common peripheral resources, here a single peripheral suchas a printer, and to avoid contention for control of the commonresources, both servers are able to seize control of the peripheral tothe exclusion of other servers, to signal other servers that control hasbeen seized, and to relinquish control of the peripheral when the jobqueue has been emptied. It is also possible for each server to checkwith other servers to determine if other servers have a pending requestfor use of the peripheral. In the case where there is a pending request,the server can relinquish control of the peripheral at the end of acurrent job even though there are jobs remaining in the job queue, so asto allow alternating use of the peripheral by each server.

FIG. 11 illustrates NEB 2 configured for multiprotocol networkoperations. FIG. 11 illustrates a combined Novell/UNIX multiprotocolenvironment, but it is to be understood that other operating protocolsmay be substituted for or used in combination with those shown in FIG.11. In FIG. 11, NEB 2 is interfaced to LAN bus 6 via electricalinterface 321, network driver 322, and link support layer ("LSL") 324,much as illustrated above in FIG. 7. Novell-specific operating protocolsare indicated at reference numerals 325, 326 and 327. More specifically,325 and 326 are an SPX/IPX operating protocol stack (or tower) by whichNovell-compatible applications programs communicate with the LAN busthrough LSL. Novell-compatible applications programs, including aNovell-compatible server such as CPSERVER, are illustrated at 327. TheNovell-compatible software drives printer 4 via bi-directional SCSI bus102 as described above.

UNIX-compatible operating protocols are illustrated at referencenumerals 335, 336 and 337. More specifically, 335 and 336 comprise aTCP/IP operating protocol stack (or tower) by which UNIX-compatibleapplication programs communicate to LAN bus 6 via LSL. UNIX-compatiblenetwork application programs, including a UNIX-compatible printer serversuch as CLPR, are designated at 337. The print server CLPR drivesprinter 4 via SCSI bus 102 as described above.

Prescan module 339 interfaces with LSL 324 to determine the frame packettype being transmitted on LAN bus 6 for each of the operating systems.In more detail, each operating system such as the UNIX operating systemand the Novell operating system can communicate on LAN bus 6 in avariety of frame packet types. When LAN bus 6 is an Ethernet type LANbus, then a UNIX operating system can communicate over the Ethernet byany of three frame packet types, namely, Ethernet 802.2, Ethernet II andEthernet SNAP. Likewise, when LAN bus 6 is an Ethernet-type bus, then aNovell operating system can communicate over the LAN bus by any of fourframe packet types, namely, Ethernet 802.2, Ethernet 802.3, Ethernet IIand Ethernet SNAP. It is possible for both the Novell operating systemand the UNIX operating system to use the same frame packet type; it isthe operating system protocols (SPX/IPX for Novell and TCP/IP for UNIX)which determine which one of the operating systems in a multiprotocolenvironment is currently communicating on the LAN bus.

In the multiprotocol environment illustrated in FIG. 11, PRESCAN module339 determines the frame packet type being used by each operating systemby repeating the steps shown in FIG. 10 for each of the operating systemprotocols (see section 4e above). For example, when Novell-compatibleand UNIX-compatible systems comprise the multiprotocol environment, thenPRESCAN simultaneously binds through LSL to all four frame packet typesfor an SPX/IPX protocol tower, so as to determine the frame packet typein accordance with the data group returned from LSL which has the properIPX header. Then, PRESCAN binds simultaneously through LSL through allthree frame packet types having a TCP/IP protocol tower. PRESCANdetermines the frame packet type being used by the UNIX-compatibleoperating system in accordance with the data group having the properTCP/IP header.

In more detail, to adaptively and automatically determine which ofplural predetermined frame packet types is currently being used for LANcommunication in a multiprotocol network environment, the PRESCANprogram module 339 is downloaded from EPROM 222 into DRAM 220 wheremicroprocessor 216 executes the PRESCAN module. To determine the framepacket type for the first operating system, PRESCAN first configures LSLto bind simultaneously to a plurality of frame packet typescorresponding to a first operating system protocol, such as SPX/IPXoperating protocol for Novell-compatible operating systems. Networkdriver 322 monitors the LAN communication bus to capture broadcasttraffic for the first operating system. In response to capturing suchbroadcast traffic, LSL provides plural data groups for the capturedbroadcast traffic, each of the data groups corresponding to a differentone of the plural packet types. The PRESCAN module 339 is reactivated toprescan each data group for the presence of a predetermined header, suchas the SPX/IPX header, and stores the frame packet type corresponding tothe data group having the predetermined header for use by the firstoperating protocol tower.

To determine the frame packet type being used for the second operatingsystem such as a UNIX operating system, PRESCAN configures LSL to bindsimultaneously to a plurality of frame packet types corresponding to thesecond operating system protocol, such as TCP/IP for a UNIX operatingsystem. The network driver monitors the LAN communication bus to capturebroadcast traffic for the second operating system, and provides pluraldata groups corresponding to the captured broadcast traffic, each of thedata groups corresponding to a different one of the packet types. ThePRESCAN module prescans each data group for the presence of apredetermined header, such as the TCP/IP header for UNIX, and stores theframe packet type corresponding to the data group having thepredetermined header.

Once knowledge of the frame packet types being used by each of theoperating systems in the multiprotocol environment has been obtained,the Novell-compatible network application programs 327, such asCPSERVER, and the UNIX-compatible network application programs 337, suchas CLPR, can both communicate on the LAN bus 6. The two applicationprograms 327 and 337 also communicate with each other as illustratedschematically by signalling line 340. Using signalling line 340, whichmay be implemented as a control register stored in DRAM which iscommonly accessed by programs 327 and 337, programs 327 and 337 cancommunicate with each other so as to signal that one of them has seizedexclusive control over printer 4 or to signal that one of them has apending request for use of printer 4, as will be described more fullyhereinbelow.

In operation, a first server such as CPSERVER, checks its operatingsystem job queue, and if there is print information in the job queue,receives the print information from its operating system. Incoordination with job queue checks by the first server, the secondserver such as CLPR checks its operating system job queue and, if thereis print information in the job queue, receives job information from theoperating system. When one of the servers has acquired sufficientinformation to require use of the printer peripheral, it seizesexclusive control of the printer, and signals to other servers viasignalling line 340 that it has exclusive control of the printer. Thisprevents contention problems whereby other servers may inadvertently tryto insert print jobs into printer 4.

The first server retains exclusive control over printer 4 until its jobqueue has been emptied. When its job queue has been emptied, the firstserver relinquishes control of printer 4 after which it may be used byany of the other servers.

Alternatively, even though the first server's job queue might not yet beempty, when the first server reaches the end of a print job, the firstserver may interrogate other servers via the signalling line 340 todetermine if the other servers have requests pending for the use ofprinter 4. If other servers have requests pending, then the first servermay temporarily relinquish control of the printer so as to permitalternating use of the peripheral by each of the servers. In this case,when the first server relinquishes control over the printer, it alsosignals that it has a pending request for use of the printer.

4g. Advertising Multiple Servers From A Single Network Node UsingSAPSERVER

As mentioned above, NetWare® only allows a single network server fromeach non-fileserver network node to advertise its services on the LANbus. However, in the multi-tasking environment established by thenon-preemptive MONITOR, NEB 2 provides more than one network server. Inparticular, NEB 2 provides the services of the print server (CPSERVER,CRPRINTER or CLPR) as well as the services of the socket server(CPSOCKET). The SAPSERVER program module allows both network servers toadvertise their services from a single network node, here the NEB, in aLAN communication system which normally supports advertising of only asingle network server from each node. SAPSERVER accomplishes this byacting as a surrogate server (or SAP'ing entity) from the NEB whichinterleavedly advertises the services of each of its client servers,here CPSOCKET and CPSERVER.

SAPSERVER listens to the network for SAP broadcast requests directed toone of its clients and responds with the server type of its client, theserver name, and a communication socket number by which the client canestablish direct LAN communication.

FIG. 12 is a view for explaining the software structure of SAPSERVER,and FIG. 13 is a flow diagram for explaining operation of SAPSERVER.

As shown in FIG. 12, SAPSERVER is positioned in the software hierarchyat the application level of software so that it can communicate directlywith the SPX and IPX network levels of software. SAPSERVER acts as asurrogate SAP'ing entity for each of its clients which in the case ofNEB 2 consists of the socket server program CPSOCKET and the printserver program CPSERVER as designated by the configuration of the board.SAPSERVER may also be configured to serve other clients as well, asillustrated diagrammatically at "CLIENT N".

As shown in FIG. 13, after microprocessor 216 retrieves the SAPSERVERprogram module from EPROM 222 and stores it in DRAM 220, microprocessor216 commences operation of the SAPSERVER program and configures it tolisten for SAP proprietary broadcasts to the SAP proprietary socket(Step S1301). In Step S1302, after microprocessor 216 retrieves theCPSOCKET module from EPROM 222 and stores it for execution in DRAM 220,the CPSOCKET program module issues a request to SAPSERVER to advertiseCPSOCKET services. In accordance with standard SAP protocol, SAPSERVERcommences periodic advertisements for CPSOCKET (Step S1303), forexample, at one minute intervals.

In Step S1304, after microprocessor 216 retrieves the CPSERVER modulefrom EPROM 222 and stores it for execution from DRAM 220, CPSERVERissues a request to SAPSERVER for SAPSERVER to advertise CPSERVERservices over the network. SAPSERVER commences periodic SAPadvertisements for the services of CPSERVER and also continues toadvertise the services for CPSOCKET. As shown in Step S1305, theadvertisements are interleaved.

Step S1306 determines whether a broadcast request has been received atthe SAP proprietary socket (e.g. socket number 453). Until a broadcastrequest has been received at the proprietary socket, SAPSERVER simplycontinues to interleavedly advertise for the services of CPSERVER andCPSOCKET. However, when a broadcast request is received at theproprietary socket then in Step S1307 SAPSERVER determines whether thebroadcast request is for the services of one of its clients, here forthe services of CPSOCKET or CPSERVER. If the broadcast request is notfor one of SAPSERVER's clients, then flow simply returns to Step S1305where SAPSERVER continues to interleavedly advertise for its clients. Onthe other hand, if the broadcast request is for one of SAPSERVER'sclients, then flow advances to Step S1308.

In Step S1308, SAPSERVER responds with an IPX packet on the proprietarysocket number 453. The IPX packet contains the server type of itsclient, the server name, and a communication socket number. The IPXpacket also designates a communication socket over which the broadcastrequestor can establish direct communication with the client. Thereupon,SAPSERVER returns to Step S1305 so as to continue to interleavedlyadvertise for each of its clients.

In Step S1309, the broadcast requester establishes direct SPX connectionwith the client designated in the broadcast request over thecommunication socket designated in Step S1308. In the presentconfiguration, where services of the print server CPSERVER is requested,the socket number is 8060. On the other hand, when requests for servicesof the CPSOCKET server is requested, the socket number is 83B4 forcommunication and 83B5 for connection. Direct communication thenproceeds as described more fully hereinbelow.

4h. Configuring The Networked Printer Using CPINIT

FIG. 14 is a flow diagram showing how a network administrator can useCPINIT from PC 14 to initialize and to configure, and later toreconfigure, both NEB 2 and printer 4 in which the NEB resides.

In Step S1401, the CPINIT utility uses a service advertising protocol(SAP) on the network to determine which networked printer devices areavailable to respond to CPINIT inquiries. At each of the NEB boards,CPSOCKET responds with server type, server name and a unique socketnumber by which each NEB can be accessed directly, and an indication ofwhether or not the NEB requires configuration.

In Step S1402, CPINIT constructs a list of all NEB's and theirassociated devices, and presents them in a menu form so that they can beselected by the system administrator. Following selection, CPINITrequests the current configuration of the targeted NEB (Step S1403).More specifically, CPINIT sends a request to the targeted NEB via theLAN interface. At the NEB, CPSOCKET, receives the request forconfiguration information from the LAN interface. CPSOCKET collects theneeded configuration information, and directs it via the LAN interfaceto CPINIT at the system administrator's PC 14 (Step S1404). In StepS1405, CPINIT displays a menu of the current configuration of thetargeted NEB.

In Steps S1406 through S1408, the system administrator specifies adesired configuration for the targeted board. More particularly,configuration is specified on the system administrator's PC 14 by meansof a user interface such as a menu display. The following configurationparameters are selected by the operator to set the configurationinformation: (1) logging information (Step S1406), (2) NEB name (StepS1407), and (3) application type (such as CPSERVER) (Step S1408).

Under logging information, the system administrator specifies one offour different levels of logging: "NONE", in which logging is disabled;"AUTO" in which basic printer usage statistics are logged once per day;"ERROR", in which basic printer usage statistics and error events arelogged as they occur; and "JOB", in which basic usage printerstatistics, error events and job start/end information are all logged asthey occur. After selecting the log preference, the system administratormust also set the maximum log size (except when "NONE" is selected) soas to permit the printer to reserve this amount of space on its disk (oron its NVRAM 111 in the event there is no printer disk or in NVRAM 228in the NEB) for storing log information.

Under NEB name information (Step S1407), the system administrator mayassign an alphanumeric name to the NEB, such as a descriptive name like"2nd Floor Laser". The descriptive name is stored by the NEB in itsNVRAM and is used by the NEB and other network devices to assist inidentification.

Under application type selection (Step S1408), the system administratorselects whether to configure the NEB as a CPSERVER or a CRPRINTER. IfCPSERVER is selected, it is necessary to designate the name of the printserver assigned to the NEB, password, application buffer size, queueservice mode, form numbers, the printer number of the printer in whichthe NEB resides, the name(s) of the print queue(s) serviced by the NEB,and the name of the primary file server. If CRPRINTER is selected, it isnecessary for the system administrator to designate the name of theprint server through which the NEB obtains its print information, theprinter number of the printer in which the NEB resides, the name(s) ofthe print queue(s) serviced by the NEB, and the name of the primary fileserver.

In Step S1409, CPINIT sends the new configuration to the NEB via thenetwork LAN. At the targeted NEB, CPSOCKET receives the newconfiguration information and stores it in NVRAM 228 (Step S1410).

To complete the configuration of the NEB, the NEB should be re-booted.The system administrator issues a command via CPINIT which in turn sendsa command to re-boot via the LAN to the targeted NEB (Step S1411). Atthe NEB, CPSOCKET receives the command to re-boot, and re-boots the NEBin the new configuration (Step S1412).

4i. Accessing the Networked Printer Using CPCONSOL

CPCONSOL is a utility program executed from the system administrator'sPC 14 by which the NEB can be used for maximum control and efficiency ofthe networked printer. Using CPCONSOL, it is possible to remotely trackroutine and ongoing maintenance parameters. For example, it can bedetermined if toner is low, if the paper tray is empty, if a page isjammed, or if the printer is not responding at all. CPCONSOL can alsokeep track of the total number of pages printed to schedule routine andpreventative maintenance, as well as plan for eventual printerreplacement.

The CPCONSOL utility gives the system administrator access to statisticsabout the printer operation as well as the efficiency of networkcommunications. CPCONSOL can determine the total number of pagesprinted, as well as the average page-per-minute rate, averagepages-per-day, and other statistics that allow monitoring of theoperating efficiency of the printer.

The network statistics allow gauging the efficiency of communications onthe network, frequency of transmit and receive errors as well asretries, overrun, and underrun errors.

When multiple printers are installed, CPCONSOL can remotely keep trackof each printer's usage, both in terms of total jobs as well as totalpages. This allows job tracking such as for direct departmental billingfor items such as consumable paper costs.

By ongoing monitoring CPCONSOL can help determine whether to relocate oradd network printers for better efficiency as well as forecast the needfor replacement.

CPCONSOL can also set up default (safe) environment parameters whichensure that the printer is configured the same way prior to each printjob (see section 4m below). The user, of course, can modify thatconfiguration within the print job itself.

FIG. 15 is a detailed flow chart showing operation of CPCONSOL. LikeCPINIT, CPCONSOL first broadcasts on the LAN to request identificationof all NEB devices attached to the LAN (Step S1501). At the NEB's,CPSOCKET responds with the unique network ID's and the communicationsocket numbers assigned to the NEB (Step S1502). CPCONSOL collects thisresponse information for all NEB's and displays a list of respondingNEB's to the administrator (Step S1503). The administrator selects oneof the NEB's whereupon CPCONSOL establishes direct network communicationwith the selected NEB by means of LAN broadcasts to the network ID andsocket numbers.

Once direct LAN communication is established with the target NEB,CPCONSOL operates by means of a user interface such as a menu display(Step S1504). The menu divides the functions of CPCONSOL into fivegroups: Environment, Network, Logging, Application Control, and PrinterStatus. These functional groups are detailed in the following sections.

Environment Group (Step S1505)

The environment selection allows CPCONSOL to display the currentenvironment of the selected printer (Step S1506), and to modify andstore the new environment (Step S1507). The environment is subdividedinto four groups: Common Environment, Interface, Control, and Quality.

Upon selecting Common Environment, CPCONSOL will initiate a LAN requestto the target NEB for the settings for Emulation Mode, Feeder, and TotalPage Count. CPSOCKET at the target NEB will receive the LAN request,obtain the desired information from its attached printer via thebi-directional SCSI interface, and send the information to CPCONSOL atthe administrator's PC 14 via the LAN interface. There, CPCONSOLdisplays a listing showing the emulation mode, the feeder, and the totalpage count.

Upon selecting the Interface menu CPCONSOL will initiate a LAN requestto the targeted NEB for interface information. When the NEB responds,CPCONSOL causes the interface listing to display the interface that iscurrently set for the selected printer.

Selecting the Control menu likewise causes CPCONSOL to initiate a LANrequest to the targeted NEB which in turn interrogates its printer viathe bi-directional SCSI bus for printer settings. The printer settingsare returned to CPCONSOL over the LAN interface which displays thecurrent settings of the printer in accordance with Table 3.

                  TABLE 3                                                         ______________________________________                                        Control Information                                                                           Description                                                   ______________________________________                                        Contrast        Printer contrast setting.                                     Timeout         This is the setting of the                                                    job time-out set in the                                                       printer.                                                      Message         Language in which messages                                                    are displayed.                                                Copy            Number of copies of each                                                      page to be printed.                                           Offset X        The offset, if any, in the                                                    horizontal direction from                                                     the upper left corner of                                                      the page, in millimeters.                                     Offset Y        The offset, if any, in the                                                    vertical direction from the                                                   upper left corner of the                                                      page in millimeters.                                          Error Skip      Displays whether the                                                          printer is set for                                                            automatic or manual error                                                     skipping.                                                     Buzzer          On or Off setting of the                                                      printer buzzer.                                               Toner Low       If the toner low, a WARNING                                                   is displayed.                                                 28-Error        Detection of Memory Full                                                      error can be turned on or                                                     off.                                                          Paper           Paper sizes that are                                                          available in the printer.                                     Current Paper   Paper cassette that is                                                        currently selected in the                                                     printer.                                                      ______________________________________                                    

Upon selecting the Quality group, CPCONSOL, after requesting andreceiving information from the targeted NEB via the LAN interface,displays the settings for Selection Mode, Refine, Memory Usage and LowResolution mode.

Network Group (Step S1508)

The network selection allows CPCONSOL to display the compiled statisticsabout the networked printer performance on the network (Step S1509), andto modify and store the new network group (Step S1510). These aresubdivided into media-dependent and media-independent related transmitand receive statistics. CPCONSOL can also clear all statistics.

When the system administrator selects the Network group, CPCONSOLinitiates a network request via the LAN interface to the targeted NEB.At the NEB, CPSOCKET, responds to the request and obtains the neededperformance information. The information is collected by CPSOCKET andreturned to CPCONSOL at the administrator's PC 14 via the LAN interface.At the administrator's PC 14, CPCONSOL displays the media-dependent andmedia-independent transmit and receive information.

Media-dependent receive and transmit statistics are summarized in Tables4 and 5.

                  TABLE 4                                                         ______________________________________                                        Media-Dependent                                                               Receive Statistic                                                                             Description                                                   ______________________________________                                        CRC             Total number of Cyclic                                                        Redundancy Check errors                                                       detected by the LBP-Remote                                    Missed Frames   Number of packets missed due                                                  to lack of space in the                                                       receive buffer, or the                                                        controller is in the monitor                                                  mode.                                                         Align Errors    Indicates that the incoming                                                   packet did not end on a byte                                                  boundary.                                                     Received Disabled                                                                             Controller was in the                                                         monitor mode.                                                 Deferring       Set when internal Carrier                                                     Sense or Collision signals                                                    are generated in the                                                          encoder/decoder.                                              Overflow        Buffer ran out of space                                                       while data was being                                                          received from the network.                                    Overruns        The buffer did not respond                                                    fast enough to keep data                                                      from flowing from the                                                         network.                                                      ______________________________________                                    

                  TABLE 5                                                         ______________________________________                                        Media-Dependent                                                               Transmit Statistic                                                                             Description                                                  ______________________________________                                        Collisions       Packet Collision Total                                       Heartbeat        Number of failures of the                                                     transceiver to transmit a                                                     collision signal after                                                        transmission of a packet                                                      with this bit set.                                           Out of Window Call                                                                             Set for the number of                                                         collisions that occurred                                                      after slot time.                                             Underruns        The buffer did not respond                                                    fast enough to keep data                                                      from flowing to the network.                                 ______________________________________                                    

Media independent statistics display the network statistics that aren'trelated to the transmission media. Such statistics are a good summary ofoverall printer activity on the network, and are summarized Table 6.

                  TABLE 6                                                         ______________________________________                                        Media Independent Parameter                                                                     Description                                                 ______________________________________                                        Abort Rx Frame    General receive problems.                                   Total Rx Frame    Total number of received                                                      frames.                                                     Rx Too Big        Receive frame larger than                                                     expected.                                                   Rx Too Small      Receive frame smaller than                                                    expected.                                                   Abort Tx Frame    General transmit problems.                                  Total Tx Frame    Total number of transmitted                                                   frames.                                                     ______________________________________                                    

Logging Group (Step S1511)

The logging group selection allows CPCONSOL to display the set ofjob-related statistics that the NEB compiles (Step S1512), and to modifyand store the new logging group (Step S1573). The displayed data includejob averages, page averages, and performance data. CPCONSOL can resetthe totals to zero with this menu as well. In addition to statistics,the NEB can create a log for every print job, write the log to a workstation disk, or clear the log file, as configured by CPINIT.

If the system administrator selects the Logging Group option, thenCPCONSOL directs a LAN request for the log file to the targeted NEB viathe LAN interface. At the NEB, CPSOCKET receives the request and, sinceCPSOCKET stores the log file on the printer, requests the log file fromthe printer via the bi-directional SCSI interface. The NEB retrieves thelog file from wherever it is stored (such as its disk 114) and providesthe file to CPSOCKET via the bi-directional SCSI interface. CPSOCKETthen puts the log file onto the network via the LAN interface forreceipt by CPCONSOL.

The log file includes values for the statistics which are divided intothree categories: Daily, Cumulative, and Average. Daily shows the valuesfor the current day. Cumulative shows the totals for all days since lastreset, or since power-on for a printer without a disk drive. Average isthe cumulative totals divided by the number of days since the lastreset. For each of the three categories, the NEB maintains totals forthe following values (unless CPINIT has set the logging level to"NONE"): days (number of days since a reset was issued or sincepower-on), pages printed, print jobs processed, off-line time, andprinting time.

CPCONSOL also retrieves the stored log file to the screen for viewingand printing. The log file is in reverse chronological order andincludes the following record types. The precise content of the log filevaries in accordance with the logging level set by CPINIT, as summarizedin Table 7.

                  TABLE 7                                                         ______________________________________                                        Type  Data                     Description                                    ______________________________________                                        STD   <Days><Pages><Jobs><Offline>                                                                           daily                                                <Printing>               statistics                                     STC   <Days><Pages><Jobs><Offline>                                                                           cumulative                                           <Printing>               statistics                                     STA   <Days><Pages><Jobs><Offline>                                                                           average                                              <Printing>               statistics                                     SOJ   <Application><User><Job> start of                                             <File server><Queue><Form>                                                                             job                                            INI   <NEB Type><ROM/MAC Address>                                                                            Initializa-                                          <Printer Name>           tion record                                    POW   <NEB Type><ROM/MAC Address>                                                                            power on                                             <Printer Name>           record                                         RBT   <NEB Type><ROM/MAC Address>                                                                            reboot                                               <Printer Name>           record                                         WAR   <Application><Warning>   warning                                        EOJ   <Application><User><Job> end of job                                           <Disposition>                                                           ERR   <Application><Error>     error                                          ______________________________________                                    

Application Control (Step S1514)

Application control allows CPCONSOL to view the current configuration ofthe NEB within the network (as either CPSERVER or CRPRINTER) (StepS1515) and to activate/deactivate or modify and store that application(Step S1516). Access to the targeted NEB is provided via the LANinterface which responds to the CPCONSOL request by putting a resultcode on the LAN interface.

Printer Status (Step S1517)

This menu allows CPCONSOL to display the current status of the printerattached to the NEB (Step S1518), and to modify and store the newprinter status (Step S1519). CPCONSOL directs a status request to thetargeted NEB via the LAN interface. At the targeted NEB, CPSOCKETreceives the status request and sends a request for the needed statusinformation to the printer via the bi-directional SCSI interface.CPSOCKET receives the status information from the printer over thebi-directional SCSI interface and directs the information back toCPCONSOL where it is displayed on the system administrator's PC 14.

There are 29 possible status conditions, "NORMAL" being the most common,as summarized in Table 8.

                  TABLE 8                                                         ______________________________________                                        Status           Meaning                                                      ______________________________________                                        NORMAL           On-line, ready to print or                                                    printing                                                     OFFLINE          Off-line, not ready to print-                                ENGINETEST       Engine test detected                                         MAINTRUNNING     Maintenance program running                                  PAPEROUT         Paper tray is empty                                          PRINTEROPEN      The printer top is open                                      PAPERJAMx        Paper is jammed at location                                                   "x"                                                          NOEPCART         No EP cartridge is present                                   TONERLOW         The toner cartridge is low                                   ULFEED           U-L feed                                                     LOADx            Your paper is loading                                        LOADnn           Load paper "nn"                                              FEEDx            Feed Paper [x = message]                                     FEEDnn           Feed paper "nn"                                              OCx              CaPSL output call                                                             [n = message]                                                SETUPPER         Set to upper tray                                            TRAYFULL         Paper output tray is full                                    PAGEFULL         The page is full                                             LINEERROR22      22 line error (see printer                                                    manual)                                                      LINEERROR40      40 line error (see printer                                                    manual)                                                      DLMEMORYFULL     Download memory full                                         WKMEMORYFULL     Working memory full                                          JOBREJECT        Job has been rejected                                        PRINTCHECK       Print check error                                            OPTREMOVAL       Option removal                                               FONTFULL         Font configuration are full                                  WARMINGUP        Printer is in warmup                                         SERVICE CALL     Service call is needed                                       TRANSIENT        A transient, unidentified                                                     error occurred                                               ______________________________________                                    

4j. NEB Responses to Status Inquiry Using CPSOCKET

CPSOCKET is an application program which runs out of DRAM 220 on the NEB2 in the multi-tasking soft-time environment provided by thenon-preemptive MONITOR. CPSOCKET causes SAPSERVER to monitor the NEB'sbroadcast socket on the LAN for broadcasts from client programs such asCPINIT, CPCONSOL and DOWNLOADER.

CPSOCKET is responsible for the internal configuration of the NEB, suchas configuration as either a PSERVER or an RPRINTER. Configurations areset at the request of CPINIT, as described above, but it is CPSOCKETthat receives those configuration commands and physically alters NVRAM228.

CPSOCKET also maintains a table of default settings for the deviceenvironment (that is, a guaranteed safe environment, see section 4mbelow), downloads the basic configuration information for the printerand for the NEB (for example, fonts and emulations) at device power-up(see section 4d above), provides device status information, statistics,and log information in response to CPCONSOL requests, and providesreset, re-boot, and firmware download capabilities.

FIGS. 16A and 16B comprise a detailed flow diagram showing operation ofthe CPSOCKET program. In Step S1601, after successful power-on-self-test(POST), microprocessor 216 transfers the CPSOCKET program module fromits storage locations in EPROM 222 into appropriate storage locations inDRAM 220. During transfer, microprocessor 216 configures the CPSOCKETprogram in accordance with the configuration information for theCPSOCKET program stored in NVRAM 228. Thus, for example, it is possibleto selectively activate certain portions of the CPSOCKET program modulein accordance with desired levels of complexity, those desired levels ofcomplexity being stored in NVRAM 228.

In Step S1602, the NEB commences execution of the CPSOCKET from DRAM220. CPSOCKET is executed in a multi-tasking soft-time environment bythe non-preemptive MONITOR which permits non-preemptive execution ofother application programs such as CPSERVER without letting oneapplication program seize control of the microprocessor to the exclusionof other application programs.

In Step S1603, CPSOCKET broadcasts its existence over the LAN interfacevia service advertising protocol broadcasts (SAPSERVER) which contain aproprietary socket number (see sectoin 4g above). Because other serversare operating in the multi-tasking environment established in StepS1602, and because the Netware®-compatible software only permits asingle non-fileserver server to advertise from a single network nodesuch as the NEB, CPSOCKET broadcasts its SAP advertisements via theSAPSERVER program. As described more fully above in paragraph 4g, theSAPSERVER program permits two network servers to broadcast from a singlenetwork node even when the network supports only single servers for eachnetwork node.

In Step S1604, CPSOCKET receives a broadcast request from a client, forexample, CPINIT or CPCONSOL on proprietary socket 453. CPSOCKET respondsto the client (Step S1605) with an IPX packet on the same socket.

In Step S1606, the client establishes direct SPX communication withCPSOCKET over a socket number that is pre-assigned to CPSOCKET, heresocket number 83B4 for communication or 83B5 for connection. Inaccordance with that direct connection, CPSOCKET receives and interpretsclient requests and/or commands that are received over the LANinterface, monitors the status of the printer over the bi-directionalSCSI interface, receives and sends status commands and/or inquiries tothe printer via the bi-directional SCSI interface, reconfigures the NEBand the NEB configuration parameters, and sends requested information tothe client via the LAN interface. These steps are described more fullybelow in connection with Steps S1607 through S1620 of FIGS. 16A and 16B.

In more detail, in Step S1607, if CPSOCKET determines that aconfiguration command has been received, then flow advances to StepS1608 in which the configuration commands are executed and the resultprovided via the LAN to the client. Configuration commands are listed inTable 9 and generally pertain to the configuration of the NEB board aseither a CPSERVER or an CRPRINTER in accordance with configurationcommands initiated by the CPINIT program.

                  TABLE 9                                                         ______________________________________                                        Configuration Commands                                                                   Data          Reference                                                       (CPINIT →                                                                            (CPSOCKET →                                   Command    CPSOCKET)     CPINIT)                                              ______________________________________                                        request for                                                                              none          current NEB settings                                 current                  (CPSERVER/                                           configuration            RPRINTER/LPR)                                        reconfigure/                                                                             Desired       new configuration                                    deconfigure                                                                              Configuration confirmation                                         activate/  none          confirmation                                         deactivate                                                                    application                                                                   reset      none          confirmation                                         re-boot    none          none                                                 ______________________________________                                    

If in Step S1609, CPSOCKET determines that a device information commandhas been received, then flow advances to Step S1610 in which thosedevice information commands are executed and the results provided to theLAN interface. In general, device information pertains to the interface,control status, font set and environmental settings of the printer 4attached to NEB 2. Device information commands in Step S1610 permitreading printer device information, setting printer device information,reading default settings for that information, and resetting the defaultsettings to desired values. Device information commands are detailed inTable 10.

                  TABLE 10                                                        ______________________________________                                        Device Information Commands                                                              Data            Response                                                      (CPCONSOL →                                                                            (CPSOCKET →                                 Command    CPSOCKET)       CPCONSOL)                                          ______________________________________                                        request for                                                                              none            interface status                                   interface                                                                     status                                                                        request for                                                                              none            printer control                                    control                    information for                                    status                     CPCONSOL                                                                      "control" menu                                     request for                                                                              none            printer font set                                   font status                                                                   request for                                                                              none            printer layout                                     layout status              (portrait/land                                                                scape, etc.)                                       request for                                                                              none            printer macros                                     quality and                                                                   common                                                                        environment                                                                   status                                                                        request for                                                                              none            printer duplex                                     duplex status              mode                                               request for                                                                              none            miscellaneous                                      miscellaneous              printer info                                                                  (collation,                                                                   stapling, paper                                                               folding, paper                                                                trays, etc.)                                       request for                                                                              none            default printer                                    default                    control                                            control                    information for                                    status                     CPCONSOL                                                                      "control" menu                                     request for                                                                              none            default printer                                    default font               font set                                           status                                                                        request for                                                                              none            default printer                                    default                    layout (portrait/                                  layout status              landscape, etc.)                                   request for                                                                              none            default printer                                    default                    macros                                             quality and                                                                   environment                                                                   status                                                                        request for                                                                              none            default printer                                    default                    duplex mode                                        duplex status                                                                 request for                                                                              none            default                                            default                    miscellaneous                                      miscellaneous              printer info                                       printer info               (collation,                                                                   stapling, paper                                                               folding, paper                                                                trays, etc.)                                       set control                                                                              new printer     confirmation                                                  control                                                                       information for                                                               CPCONSOL "control"                                                            menu                                                               set font   new printer layout                                                                            confirmation                                                  (portrait/landscap                                                            e, etc.)                                                           set quality                                                                              new printer macros                                                                            confirmation                                       and common                                                                    environment                                                                   set duplex new printer duplex                                                                            confirmation                                                  mode                                                               set        new miscellaneous                                                                             confirmation                                       miscellaneous                                                                            printer info                                                       printer info                                                                             (collation,                                                                   stapling, paper                                                               hold, paper trays,                                                            etc.)                                                              set default                                                                              default printer confirmation                                       control    control                                                                       information for                                                               CPCONSOL "control"                                                            menu                                                               set default                                                                              default printer confirmation                                       layout     layout (portrait/                                                             landscape, etc.)                                                   set default                                                                              default printer confirmation                                       quality and                                                                              macros                                                             common                                                                        environment                                                                   set default                                                                              default printer confirmation                                       duplex     duplex mode                                                        set default                                                                              default         confirmation                                       miscellaneous                                                                            miscellaneous                                                      printer info                                                                             printer info                                                                  (collation,                                                                   stapling, paper                                                               holding, paper                                                                trays, etc.)                                                       ______________________________________                                    

If in Step S1611, CPSOCKET determines that a configuration parametercommand has been received, then flow advances to Step S1612 in whichCPSOCKET executes the received command and provides the result via theLAN to the client. As shown in Table 11, configuration parametercommands pertain generally to parameter values stored in the NEBconcerning time, date, safe printer environment information, loggingoptions, log file size, etc.

                  TABLE 11                                                        ______________________________________                                        Configuration Parameter Commands                                                          Data          Response                                                        (CPINIT →                                                                            (CPSOCKET →                                  Command     CPSOCKET)     CPINIT)                                             ______________________________________                                        request for none          configuration                                       current                   parameters (e.g.                                    configuration             time, data, safe                                    parameters                printer environment                                                           info, logging                                                                 options, etc.)                                      set new     configuration confirmation                                        configuration                                                                             parameters (e.g.                                                  parameters  time, data, safe                                                              printer envirorment                                                           info, logging                                                                 options, etc.)                                                    ______________________________________                                    

If in Step S1613 CPSOCKET determines that a NEB application programcommand has been received, then flow advances to Step S1614 in whichCPSOCKET provides information on the current application program, namelyRPRINTER, PSERVER, or LPR (for UNIX). Application program informationgenerally includes server name, file server queue, device ID, etc., asdetailed in Table 12.

                  TABLE 12                                                        ______________________________________                                        Application Program Information                                                          Data            Response                                                      (CPINIT →                                                                              (CPSOCKET →                                 Command    CPSOCKET)       CPINIT)                                            ______________________________________                                        request for                                                                              none            CRPRINTER info                                     CRPRINTER                                                                     info                                                                          set CRPRINTER                                                                            new CRPRINTER info                                                                            confirmation                                       info                                                                          request for                                                                              none            CPSERVER info                                      CPSERVER info                                                                 set CPSERVER                                                                             new CPSERVER info                                                                             confirmation                                       info                                                                          request for                                                                              none            CLPR info                                          CLPR info                                                                     set CLPR info                                                                            new CLPR info   confirmation                                       ______________________________________                                    

If in Step S1615 (FIG. 16B) CPSOCKET determined that a NEB/printerstatistic command has been issued, then flow advances to Step S1616 inwhich CPSOCKET interrogates the printer through the bi-directional SCSIinterface to obtain needed printer statistics. The statistics correspondto the network group displays described above in connection withCPCONSOL, as well as to print job statistics such as the total number ofpages printed, the total number of jobs, the total number of off-linetime, etc. The job statistics correspond to the logging group describedabove in connection with the CPCONSOL program. Specific examples of thecommands executed in the NEB/printer statistics commands are set forthin Table 13.

                  TABLE 13                                                        ______________________________________                                        Statistics Commands                                                                      Data          Response                                                        (CPCONSOL →                                                                          (CPSOCKET →                                   Command    CPSOCKET)     CPCONSOL)                                            ______________________________________                                        request    none          network statistics                                   network                  for CPCONSOL                                         statistics               "NETWORK" menu                                       clear      none          confirmation                                         network                                                                       statistics                                                                    request job                                                                              none          job statistics for                                   statistics               CPCONSOL                                                                      "LOGGING" menu                                       clear job  none          confirmation                                         statistics                                                                    ______________________________________                                    

If in Step S1617 CPSOCKET determines that a logging command has beenreceived, then flow advances to Step S1618 in which CPSOCKET obtains thelog file from the printer disk 114 via the bi-directional SCSIinterface, and sends the log file to the client via the LAN interface.Logging commands are summarized Table 14.

                  TABLE 14                                                        ______________________________________                                        Logging Commands                                                                         Data          Response                                                        (CPCONSOL →                                                                          (CPSOCKET →                                   Command    CPSOCKET)     CPCONSOL)                                            ______________________________________                                        request    block #       next block number of                                 log file                 log file and log data                                clear log  none          confirmation                                         request                                                                       ______________________________________                                    

If in Step S1619 CPSOCKET determines that a download command has beenreceived from the LAN interface, then flow advances to Step S1620 inwhich CPSOCKET executes the download request, for example, by receivingdownloadable code and storing it in specified locations in DRAM 220, byproviding checksum data for the downloadable code, and by flashing thedownloadable code into EPROM 222. Some of the more important downloadcommands are summarized in Table 15.

                  TABLE 15                                                        ______________________________________                                        Download Commands                                                                          Data          Response                                                        (DOWNLOAD →                                                                          (CPSOCKET →                                 Command      CPSOCKET)     DOWNLOAD)                                          ______________________________________                                        download     code          confirmation                                       request                                                                       call request checksum,     confirmation                                                    starting address                                                 flash EPROM  checksum      confirmation                                       ______________________________________                                    

4k. Logging Peripheral Statistics

As described earlier with respect to FIG. 5A, Steps S9 through S12comprise an automatic logging function in which peripheral statistics(e.g. number of pages printed per day) and error events areautomatically logged (stored) for later retrieval; and wherein thelogging level (statistical resolution) may be varied by the networkadministrator. In general, the network administrator may select alogging level, and then extract printer statistics and error events fromthe log file at any time. The network administrator's portion of suchfunctions has been described above in paragraph 4i, and reference may behad to the discussion and tables set forth therein, especially Table 7which indicates the content of the log file depending upon the logginglevel set by CPINIT.

As background, few LAN peripherals maintain their own statistics, butthe NEB 2 includes the capability of logging the current status anddaily statistics of printer 4 at midnight of each day. This relieves thesystem administrator from having to remember to do this on a dailybasis. The status and statistics data may be stored in printer hard disk114, printer NVRAM 111, NEB DRAM 220, or in the NEB NVRAM 228. Thelocation of the stored log file may be selected by the networkadministrator depending upon the remaining memory capacity of each ofthose memories, and the statistics required by the logging levelselected by the network administrator. For example, if the printer has ahard disk, the network administrator may choose the fairly-detailed"JOB", logging level so that voluminous statistics may be retained. Onthe other hand, if the printer has no hard disk, the networkadministrator may choose the less-detailed "ERROR" logging level so thatless storage space is required. If the log file is filled, new errordata will merely wrap around in the memory replacing old error data withnew error data.

The NEB will automatically store printer statistics such as pagesprinted, jobs printed, off-line time, and print time each night foraccess for the system administrator at a later time. The statistics canbe used to anticipate replacement of consumable printer supplies, suchas toner, and to monitor user behavior such as leaving the printeroff-line for extended periods of time.

In general, the logging function is accomplished by the printercontroller board always knowing what time it is. When aprinter/controller board is first powered on, the board finds thenearest server and requests the time. The board continues to do thisevery minute. When the day of the week changes, the board automaticallyrequests the printer to report its page count. The board then calculatesthe daily statistics and stores them either to the printer hard disk orto the board NVRAM. These statistics are stored and available to theexternal network program CPCONSOL that can display them to a screen orsave them to an external file.

As described above in paragraph 4i, the network administrator may selectfour logging levels: NONE; AUTO; ERROR; and JOB. At the NONE level, nologging statistics are maintained (although they may still be calculatedevery minute and temproarily kept in NEB DRAM 220). At the AUTO level,daily statistics are maintained for printer features such as printingdays, pages, jobs, off-line time, and print time. The number ofcumulative pages printed is determined by the printer, but the otherstatistics are determined by the NEB.

The ERROR logging level maintains the daily statistics discussed above,and also error conditions in the printer and also errors that occur inan application (i.e. CPSERVER). The NEB queries the printer every minutefor such error conditions. Such printer error conditions may include:off-line; out-of-paper; printer-is-open; paper-jam; no-toner-cartridge;toner-is-low; printer feed and load errors; tray-is-full; line errors;print-job-rejected; font-is-full; service call; etc. Application errorsmay include: fileserver down; primary fileserver unavailable; CPSERVERrunning elsewhere; IPX not installed; etc.

The JOB logging level maintains the daily statistics and errorconditions noted above and also maintains job start and job endinformation, which are determined by the NEB. Of course, the number andtypes of logging levels, and the data retained in each logging level maybe varied according to the particular peripheral and the particular LANin which the NEB is installed.

FIGS. 17A and 17B comprise a flow chart showing the overall operation ofthe automatic logging function within the NEB. Reference may also be hadto FIG. 5A and Table 7 noted above. At Step S1, power is applied to theNEB and at Step S8, the timer module finds the nearest server andrequests the time. At Step S1701, it is determined whether the NONElogging level has been selected. If the NONE logging level has beenselected, the process skips to the end of the flowchart where a returnis made to the overall flow diagram of FIGS. 5A, 5B and 5C.

If the NONE logging level has not been chosen in Step S1701, Step S1702determines whether the AUTO logging level has been selected. If the AUTOlogging level has been selected, the process proceeds to Step S9 wheremidnight is awaited. However, if the AUTO logging level has not beenselected, Step S1703 determines whether the ERROR logging level has beenselected. Where the ERROR logging level has been selected, the processskips to Step S1706 where a one minute timeout is awaited. However, ifthe ERROR logging level has not been selected, it is determined in StepS1704 that the JOB logging level has been selected. In this case, StepS1705 stores the job start and job end times to the log file. At StepS1706, a one minute timeout is awaited whereafter Step S1707 queries theprinter for error events and saves such events to the log file. Thus,when either the ERROR or JOB logging levels have been selected, theboard queries the printer every minute for error events and stores sucherror events in the log file.

Step S9 waits for midnight whereupon the NEB queries the printer for itsdaily statistics at Step S10 FIG. 15B). If midnight has not been reachedin Step S9, the procedure returns to Step S1702 where it is determinedwhich logging level has been selected.

In Step S11, the daily printer statistics are calculated utilizing theprinter statistics received in Step S10. Thereafter, in Step S12, thedaily statistics and the error events are stored in the printer harddisk 114 and/or the printer NVRAM 111, and/or the NEB NVRAM 228. Notehere that the network administrator may select to store loggingstatistics and error events in any combination of memories, providingfurther flexibility to the LAN.

The logging functions discussed above are quite significant in makingthe printer an interactive and responsive member of the LAN since theSCSI connection between the NEB and the printer is capable of extractingvolumes of specific data from the printer.

4l. Multi-tasking Independently Executable Programs

As briefly described earlier with respect to Step S20 of FIG. 5B, theNEB EPROM 222 stores a MONITOR program which is a mechanism whichsupports multi-tasking in the run-time environment while permittingsynchronous operation in a de-bug environment. MONITOR permitscurrently-called tasks to be performed on a non-preemptive basis whilethe NEB awaits real-time interrupts from either the LAN (for CPSERVER orCPSOCKET) or through the SCSI interface (e.g., when status informationis being provided from the printer to the NEB in response to apreviously-received status request from the LAN). Thus, MONITOR permitsall currently-executing tasks to be performed simultaneously by sharinguse of the microprocessor 216. Of course, all soft-time applications,including MONITOR itself, are interruptable by real-time events.

FIG. 18 is a notional flowchart of a sequence of events which may occurin order to illustrate the multi-tasking operation within the NEB. AtStep S1, power is applied to the NEB, and the MONITOR program isdownloaded from EPROM 222 to DRAM 220 in Step S1801. For example, thefollowing modules are downloaded together with MONITOR: SCSI Driver;Link Support Layer; Network Driver; Prescan; IPX/SPX; Customized NETX;SAPSERVER; CPSOCKET; and Print Applications (see FIG. 6).

If, at Step S1802, print data is received from file server 30, CPSERVERwill begin processing the received job data in preparation fortransmission to the printer 4. Processing of such print information isnow in the "soft-time" environment, and Step S1803 determines whether arelinquish interrupt has been received from the program processing theprint data. If a relinquish interrupt has been reached at Step S1803,execution of the currently-executing module is stopped and control isreturned to MONITOR at Step S1804. MONITOR saves the state of theinterrupted task in DRAM 220. However, if the relinquish interrupt hasnot been reached at Step S1803, the process proceeds to Step S1805 whereit is determined whether the currently-executing module has reached anend. If the end has not been reached in Step S1805, the program waitsuntil another relinquish interrupt is reached in Step S1803.

If the currently-executing module has been stopped at Step S1804, or ifthe currently-executing module has reached an end at Step S1805, it isdetermined at Step S1806 whether data has been received which requiresthe execution of another software module, e.g., where data is receivedover the SCSI interface in response to a previously-issued request forprinter status. If it is determined in Step S1806 that such data hasbeen received, Step S1807 begins execution of another application moduleusing the newly-received data.

At Step 1808, it is determined whether a relinquish interrupt has beenreached in the second application module. If such an interrupt has beenreached, the second application will stop execution and pass control toMONITOR which stores in DRAM 220 the state of the just-interruptedsecond module at Step S1809. However, if the relinquish interrupt in thesecond module has not been reached at Step S1808, it is determined atStep S1810 whether the end of the second module has been reached. If theend has not been reached, the program merely awaits the relinquishinterrupt at Step S1808. If it is determined that the second module endhas been reached in Step S1810, Step S1811 determines whether the firstmodule end has been reached. Where the end of the first module has notbeen reached, but the end of the second module has been reached, theprocess returns to waiting for a relinquish interrupt in the firstapplication module at Step S1803. If both the first and second moduleshave reached their end at Step S1811, control will return to the MONITORprogram in order to execute other newly-received soft-time tasks.

After the second application module has stopped executing due toreaching a relinquish interrupt therein, control is passed to MONITORwhich, after storing the state of the interrupted module in DRAM 220(Step S1809), will recommence execution of the first module in StepS1812, and continue execution of the first module until another firstmodule relinquish interrupt is reached at Step S1803.

Thus, the non-preemptive multi-tasking allocation of the microprocessorresources allows processing of a number of tasks in parallel on a nearreal-time basis.

4m. Placing the Printer in a Default Configuration

As discussed above with respect to Step S25 in FIG. 5C, the NEB willensure that the printer is set to a known, default configuration at thebeginning or end of a print job. The NEB does this by downloading to theprinter's non-volatile memory (either hard disk 114 or NVRAM 111) adefault configuration code which indicates the default environment (e.g.portrait mode, 10 point type, Roman lettering, etc.) in which theprinter should be left at the conclusion of a print job. Upon receivinga print data stream from the LAN, the NEB retrieves the configurationcode from the printer's non-volatile memory, appends the configurationcode to a block of print data as an escape sequence, and then downloadsthe print job block with appended escape sequence to the printer. Theprinter will then conduct a printing operation, and (based on the escapesequence) will leave the printer in the desired default configuration.

Novell NetWare® software includes the ability to reset a network printerin a default environment after every print job. It does this by havingthe file server 30 install what amounts to a fake print job at the headof the print job itself. However, the exact printer escape sequencesnecessary to set particular printer default configurations reside in adatabase on the network, and not within the printer itself. Therefore,if it is desired to operate UNIX on the LAN, or where there is a problemwith the file server itself, the printer may not be restored to adefault configuration which ensures that the next print job will beprinted with the printer in a known configuration.

A method of guaranteeing a printer default environment using the NEBoperates on the difference that the printer reset state configurationand requisite escape sequence instructions reside within the printeritself, and the printer itself is responsible for resetting its ownenvironment within print jobs. Thus, the printer reset feature isavailable without depending upon any device external to the printer.Furthermore, the initial default configuration may be loaded andsubsequently modified from a remote location over the LAN through theNEB's serial or parallel interfaces.

The configuration code may be sent to the NEB through the CPCONSOLprogram, as discussed above in section 4i.

It may be convenient to store a plurality of default configuration codesin the printer non-volatile memory in order to allow the networkadministrator great flexibility for printer usage on the LAN. Forexample, print jobs received from an engineering source may require theprinter to default to a portrait mode, whereas print jobs received fromaccounting may require that the printer be left in a spread sheet mode.Thus, by ensuring a known default environment, any of a number of LANsources may utilize the printer for their specific jobs.

FIG. 19 depicts a more detailed flowchart for setting the printerdefault configuration. At Step S1, power is applied to the NEB, and atStep S22, the NEB accesses the LAN file server for active print queuesand downloads print data to the DRAM 220.

If the printer non-volatile memory stores more than one defaultconfiguration code, it may be necessary to first determine what type ofdata is being transmitted from the LAN in order to determine whichdefault configuration the printer should be left in. Therefore, StepS9101 determines the LAN source of the print job, and Step S1902retrieves the appropriate default configuration code from the printer,which code corresponds to the determined LAN source.

At Step S1903, the NEB assembles blocks of image data and designates astart-of-print-job and an end-of-print-job for each print job. At StepS1904, the NEB microprocessor 216 appends to a print job an escapesequence which corresponds to the retrieved configuration code.Preferably, the escape sequence is appended to the beginning of theprint job, but it may be appended to the end of the print job, or toboth the beginning and end of the job. Then, at Step S1905, the printjob, with appended escape sequence, is transferred to the printer, andthe printer then renders print according to the received print job. Whena print job is completed after Step S24, the printer will set itself toa default environment at Step S25, which environment corresponds to thedefault configuration code retrieved in Step S1902. Therefore, theprinter will be left in a default environment which ensures that thenext print job will begin with the printer in a known configuration.

Thus, a robust and efficient hardware and software solution has beenfound for ensuring that the printer itself stores a defaultconfiguration and is responsible for placing itself in a defaultcondition at the end of every print job.

4n. Downloading Executable Files into the NEB from a Remote LAN Location

The downloading of executable files from the LAN to DRAM 220 will bediscussed in more detail with respect to the flow diagram in FIG. 20,and with respect to the discussion above of Step S30 in FIG. 5C.

NEB 2 is configured initially prior to shipping. However, NEB 2 can bereconfigured subsequently by sending updated executable files across theLAN from the network administrator's PC 14 to the NEB 2. Furthermore,network administrator can remotely alter the executable files stored inDRAM 220 of NEB 2, as desired.

The process by which executable files can be altered in DRAM 220 will bediscussed in detail with respect to FIG. 20.

After the board has been powered-up at Step S1, the flow proceeds toStep S2001 at which point the network administrator activates aDOWNLOADER program to broadcast over the LAN a request foridentification of all NEB devices having a particular configurationwhereupon flow advances to Step S2002.

In Step S2002, the DOWNLOAD program determines whether any target NEBshave responded. If in Step S2002 it is determined that no target NEBshave responded, flow returns to Step S2001 in which the DOWNLOAD programrebroadcasts the request with new target information and then flowadvances to Step S2002.

If in Step S2002 a target NEB responds, flow advances to Step S2003.

In Step S2003, the SAPSERVER program responds with the unique networkIDs and the unique socket numbers assigned to each NEB (see section 4gabove). This location information is collected, the networkadministrator selects a particular NEB to download an executable file,and communication is established with the target NEB.

Upon selecting the target NEB, the network administrator downloads newoperational files and a spetial packet containing a checksum value toDRAM 220 across the LAN in Step S2004 whereupon flow advances to StepS2005.

In Step S2005, microprocessor 216 performs a checksum operation on thenewly loaded operational files and compares the checksum value with achecksum value sent in the special packet which is stored in DRAM 220after the operational files have been stored.

If the checksum value does not equal the checksum value in the specialpacket, then flow advances to Step S2006 at which point microprocessor216 notifies the network administrator that the checksum value for thenew operational files is incorrect and at which point microprocessor 216may purge the files from DRAM 220.

If in Step S2006 the checksum value is verified, then flow advances toStep S2007 at which point the executable files are acted on bymicroprocessor 216.

Thus, the network administrator can alter the operation of NEB 2 byremotely sending new operational files to be stored and to be executedfrom DRAM 220.

4o. Loading Independently Executable Modules in ROM

As described above in FIG. 5C with respect to Step S32, when a binaryROM image is to be loaded into EPROM 222, a plurality ofindependently-executable modules are assembled, ordered, and preparedfor flash to EPROM 222. The assembly and ordering of the modules ispresently carried out on a DOS PC, but may be carried out in the NEBitself. An advantage of assembling the independently executable modulesin a PC is that the modules may be constructed and/or modified in a DOSenvironment.

NEB firmware comprises a number of separately linked modules, one ofwhich contains permanently ROM-resident code which receives control atpower-up and provides self-test, loading of other modules into DRAM 220,and basic I/O services. The other modules residing in the EPROM 222 mustbe copied to DRAM 220 before execution. There are two types of suchmodules, the first of which includes programs which are essentiallydrivers which receive control when loaded, initialize, and then exit,remaining resident. The second type of such modules are applicationprograms, each of which executes a specific set of functions.

In FIG. 21, the NEB is powered-up at Step S1. At Step S2101, a utilityresident in the PC reads from its RAM a configuration file containingthe names of all modules to be placed in the ROM image. Theconfiguration file is used to select from RAM, at Step S2102, thosemodules which are going to be flashed to EPROM 222.

At Step S2103, the utility writes a header for the first module, theheader identifying that module, describing the module attributes, andincluding a pointer which points to the immediately succeeding module.This pointer aides in the ordering of the modules in a specific orderprior to loading. At Step S2104, it is determined whether the lastmodule identified by the configuration file has been selected. If thelast module has not been selected, the process loops to Step S2103,where the header is written for the next module.

When the last module has been selected in Step S2104, the utilityappends the ROM-resident code to the end of the image program (at StepS2105) so that upon power-up, the initialization code resides at theaddress expected by microprocessor 216.

When the ROM binary image is thus constructed, the image may bedownloaded to one portion of the memory area of NEB DRAM 220, and thenflashed to EPROM 222, as will be discussed in greater detail in section4q below and with respect to the detailed discussion of FIG. 5C, StepS36.

4p. Protecting the EPROM During a Flash Operation

FIG. 22 is a block diagram showing the functional construction of theEPROM flash protection circuitry resident on the NEB. The EPROM flashprotection circuit includes microprocessor 216 coupled to data bus 250and address bus 251. Also connected to data bus 250 and address bus 251is DRAM 220. DRAM 220 is capable of storing a ROM firmware imagedownloaded from a remote LAN device into one portion of its memory area(see section 4o above), and application process steps into anotherportion of its memory area. Also coupled to data bus 250 and address bus251 are EPROM 222, latch 252, and PAL 253. D-type flip-flop 254 isconnected to latch 252 and PAL 253. During operation, flip-flop 254receives as its clock input an output signal from PAL 253 and as itsdata input, an output signal from latch 252. Latch 252 and PAL 253 arealso connected to DC--DC converter 212, and DC--DC converter 212 isconnected to transistor switch 255. When activated by latch 252, DC--DCconverter 212 sends +12 volts to the input emitter of transistor switch255. Flip-flop 254 is also connected to transistor switch 255 to providethe necessary input to open/close switch 255.

The operation of the EPROM flash protect circuitry will now be explainedin more detail with reference to FIG. 22. Upon power-up, output of latch252 will be low and flip-flop 254 will be reset. In this manner, theoutput signal PROG1 from latch 252 will be low and voltage from DC--DCconverter 212 will be directed to sink current to a ground state. Atpower-up, flip-flop 254 is reset so that its output is set low therebyopening transistor switch 255.

With transistor switch 255 in an open state, Vpp pin of EPROM 222 willbe held at 0 volts preventing any data from being accepted or a flashoperation from being performed. That is, for a flash operation to occurin EPROM 222, the Vpp pin must reach a level of at least +11.4 volts,which is a requirement set by the EPROM manufacturer's specifications.However, in order to achieve this voltage level, the following twoprogramming steps are required.

First, when a new ROM firmware package is received in DRAM 220,microprocessor 216 receives a command to flash EPROM 222, by generatingan I/O write to address 360 hex with data bit 7 high (80 hex). In thismanner, DC--DC converter 212 can be first turned on.

As shown in Tables 16 and 17, address 360 hex corresponds to controlregister 230 which is used to control read/write operations to NVRAM228. As shown in Table 17 below, when 360 hex is sent with bit 7high/low, the address corresponds to an operation of DC--DC converter212.

                  TABLE 16                                                        ______________________________________                                        I/O SELECT         ADDRESS                                                    ______________________________________                                        LAN CHIP           300 - 30F HEX (R/W)                                        DMA DATA LATCH     310 - 317 HEX (R/W)                                        LAN CHIP SOFT RESET                                                                              318 - 31F HEX (R)                                          SCSI CHIP REGISTER 320 - 32B HEX (R/W)                                        STATUS REGISTER    330 HEX (R)                                                CONTROL REGISTER #1                                                                              360 HEX (R/W)                                              ______________________________________                                    

                  TABLE 17                                                        ______________________________________                                         ##STR1##                                                                     ______________________________________                                    

After address 360 hex is output, microprocessor 216 generates an I/Owrite command and sends a write select to PAL 253. PAL 253 detects avalid address, decodes it and activates latch 252. With bit 7 high inaddress 360 hex, the PROG1 signal is set high and output from latch 252to DC--DC converter 212. When the PROG1 signal is received at DC--DCconverter 212, it operates DC--DC converter to produce +12 volts. The+12 volts from DC--DC converter 212 is sent to transistor switch 255,and which remains at its emitter until transistor switch 255 is closed.

However, before +12 volts is allowed to pass through transistor switch255, the second step must be executed. That is, microprocessor 216outputs an I/O read command and outputs address 366 hex whichcorresponds to a PAL address. When microprocessor 216 generates both thecommand and address, PAL 253 decodes the address and generates a PROG2signal. When the PROG2 signal is high, it will provide a clock input toflip-flop 254.

Upon receiving the clock input, flip-flop 254 will input the PROG1signal from latch 252 and then generate a TRANSON signal at its output.The TRANSON signal is output to transistor switch 255 which operates toclose the switch that allows +12 volts at its emitter to pass through toits collector. At this point, +12 volts is sent from the collector oftransistor switch 255 to the Vpp pin of EPROM 222.

With +12 volts placed at the Vpp pin of EPROM 222, microprocessor 216sends out an EPROM select signal. In order to prevent the new firmwareimage from being corrupted, EPROM 222 must first be cleared and erased.Then the EPROM 222 is flashed with the new ROM firmware image stored inDRAM 220. Once the new ROM firmware image is stored in EPROM 222, NEB 2can be re-booted from the new ROM firmware image.

The operation of the EPROM protection circuit will now be explained withreference to FIG. 22 and the flowchart of FIG. 23.

In Step S2301, a new ROM firmware image is received by NEB 2 across theLAN and loaded into DRAM 220. Microprocessor 216 receives a command toflash EPROM 222 in Step S2302. In Step S2303, microprocessor 216 sendsout an I/O write command to PAL 253 and outputs address 360 hex with bit7 high. Flow advances to Step S2304 in which bit 7 high activates latch252 to output the PROG1 signal. The PROG1 signal turns on DC--DCconverter 212 and +12 volts is output to transitor switch 255. In StepS2305, microprocessor 216 sends both an I/O read command to PAL 253 andaddress 366 which is a PAL address. In response, PAL 253 outputs thePROG2 signal to clock flip-flop 254 which allows the PROG1 signal to beinput at its data input. Flip-flop 254 outputs the TRANSON signal totransistor switch 255 which allows +12 volts to pass from the collectorof transistor switch 255 to the Vpp pin of EPROM 222. In Step S2306,microprocessor 216 clears and then erases EPROM 222. In Step S2307,microprocessor 216 determines if EPROM 222 has been completely erased.If EPROM 222 is not completely erased, flow returns to Step S2307.

After microprocessor 216 determines that EPROM 222 has been completelyerased, in Step S2308, the ROM firmware image is downloaded from DRAM220 to EPROM 222. Once the ROM firmware image is successfully loaded, inStep S2309 microprocessor 216 writes address 360 hex with bit 7 low. ThePROG1 signal from latch 252 goes low and DC--DC converter 212 allows thevoltage level to sink current to a ground state.

In Step S2310, microprocessor 216 sends PAL 253 an I/O read command anda 366 hex address which permits the PROG2 signal to go low therebyclocking the flip-flop which outputs a low TRANSON signal which operatesto open transistor switch 255.

Thus, in Steps S2309 and S2310, +12 volts is removed from Vpp pin ofEPROM 222 and the flash operation is ended. After the flash operation,microprocessor 216 determines if a re-boot command has been received inStep S2311. If the re-boot command has been received, NEB 2 is re-bootedin Step S2312 from the new ROM firmware image in EPROM 222. However, ifno re-boot command is received, then flow ends.

4q. Remotely Altering Firmware

The method for remotely altering firmware in EPROM 222 will be discussedin more detail below and with reference to the flowchart illustrated inFIG. 24, Step S36 of FIG. 5C, and section 4i above.

Prior to shipping a NEB to a customer, the NEB is configured with theminimum number of executable files which permit the NEB to performnecessary functions. However, the NEB can be reconfigured subsequentlyby the customer. That is, a network administrator may download data froma remote LAN device, which data may contain anything from a patch code,to manufacturing test routines, to entire firmware updates to bedownloaded to the EPROM.

In more detail, NEB2 can be reconfigured by sending executable filesacross the LAN from the network administrator's PC 14 to NEB 2. Thenetwork administrator can remotely alter the ROM firmware image in EPROM222, as desired.

In Step S2401, the network administrator activates a CPFLASH programthat uses a MAC address as a command line parameter to target a specificNEB. CPFLASH issues a SAP broadcast request which is responded to bySAPSERVER running on the NEB. In Step S2402, CPFLASH waits for aresponse from the targeted NEB. If in the case where the targeted NEBdoes not respond in approximately 15 seconds, the flow returns to StepS2401 and the broadcast is resent. However, in the case where thetargeted server responds, flow advances to Step S2403.

In Step S2403, the address and location of the targeted NEB is received,communication with the NEB having the matching MAC address isestablished, and a new ROM image firmware is downloaded over the LAN toDRAM 220.

In Step S2404, the validity of the ROM firmware image is checked beforeproceeding to the next step. The validity of the ROM firmware image isverified against an image checksum which is sent in a special packetalong with the download operation in Step S2403. If the checksum valuedoes not match the checksum downloaded with the ROM image, then in StepS2405 the operator is notified of an error and the ROM firmware image inDRAM 220 is purged.

If the checksum value is valid, then flow advances to Step S2406 atwhich point microprocessor 216 retrieves any data which is to bepreserved, such as the MAC address, and stores the data within theproper locations in the new firmware image stored in DRAM 220. In thisfashion, if the new ROM firmware image is defective, the NEB may stillfunction since predetermined portions of essential ROM firmware aremaintained. Once the essential portions of ROM firmware are preserved,flow advances to Step S2407 at which point EPROM 222 is controlled to becleared and erased a plurality of times, if requried. After EPROM 222has been erased, in Step S2408 the new ROM image is loaded into EPROM222.

After the flash operation, microprocessor 216 determines if a re-bootcommand has been received in Step S2409. If the re-boot command has beenreceived, NEB2 is re-booted in Step S2410. However, if no re-bootcommand is received, then flow ends.

In Step S2404, the validity of the ROM firmware image may also beverified by comparing newly received firmware data with data previouslystored in EPROM 222. For example, where EPROM 222 stores hardwareindicators previously carried by PROM 232 (e.g., board manufacture date,board revision number, manufacturing facility, etc.; to be discussed ingreater detail in section 5 below), such indicators may be compared withthe same indicators in the newly-received ROM firmware image. Thiscomparison may be made in addition to or in lieu of the checksumcomparison discussed above.

It is noted that a new MAC address may also be flashed into EPROM 222 atthe same time a ROM firmware image is flashed. However, it is preferableonly to flash a MAC address prior to shipping, at the completion of NEBtest. This feature is discussed in more detail with respect to Section 5below.

5. TEST

Prior to installing the NEB in the printer, it may be tested to ensurethe integrity of its hardware and software components. FIG. 25 depictsone test configuration which may be utilized to test the NEB 2. In FIG.25, the NEB 2 is coupled to PC1 300 via a cable 302 coupled to the NEBserial port 218. A printer 304 may be coupled to PC1 300 in order toprint out test results.

The NEB 2 is coupled to a test driver PC2 306 through an SCSI bus 308and Ethernet LAN connections 310, 312. The PC2 306 includes an SCSIboard 314 and a network controller board 316 so that it may simulate aprinter and LAN entities (such as the network administrator's PC 14).The PC2 will act as a transponder, receiving and returningcommunications to and from the NEB 2, as commanded by the test programsinput to the NEB from PC1 300 through the serial port 218.

After power is applied to NEB 2, it performs the power-on-self-testoperation. While the NEB 2 is performing each test operation in thePOST, PC1 300 receives test checkpoint results across serial cable 302.

Once it is determined that NEB 2 has satisfactorily completed POST, NEB2 enters a "Ready For Download" state. In this state, NEB 2 waits for aperiod interval of approximately one second for further inputinstructions across any one of the input ports.

While the NEB is in the download state, PC1 300 uploads test programs tothe NEB through serial port 218. As NEB 2 completes execution of eachtest program, it sends each test result back to PC1 300 forverification. If the next checkpoint is not received within a timeoutperiod (e.g., 1 second), it is determined that an error has occurredduring the NEB test program, and an error signal is output by PC1 300.The error signal may he indicated on a display at PC1 300, or printedout on printer 304.

On the other hand, if the next checkpoint received by PC1 300 is notverified, then PC1 300 rescripts the test program (by adding further,more detailed test modules) in accordance with the received result. Inthis manner, PC1 300 can locate the problem and debug NEB 2.

Some test programs may require NEB 2 to communicate with PC2 306 overeither the SCSI bus 308 or one of the LAN connections 310, 312. Forinstance, in accordance with the test program, NEB 2 may request datafrom PC2 over the LAN connection 310. PC2 306 is configured to returnappropriate responses to each communication from NEB 2, therebyeffectively emulating the printer and the other LAN members. If thecorrect communication is returned from PC2 306, NEB 2 indicates asuccessful test by passing another checkpoint to PC1 300 through theserial port 218.

A more detailed discussion of the method for testing NEB 2 will heprovided below with reference to the flowchart illustrated in FIGS. 26Aand 26B, and in accordance with the test configuration depicted in FIG.25.

When power is first applied to the NEB 2, NEB 2 executes the POSTprogram from EPROM 222, in Step S2601. The POST program includesindividual programs for testing component operation and softwareprogramming. After execution of an individual programs within POST, inStep S2602 a checkpoint is sent to PC1 300 to be verified. If acheckpoint is not sent after a predetermined period following theexecution of an individual program or a returned checkpoint isincorrect, an error signal is sent out from PC1 300 in Step S2603.However, if all checkpoints are correct and received within a timelyfashion, the process advances to Step S2604 where PC1 300 prepares tosend test programs to the NEB.

At Step S2605, the POST program is complete and NEB 2 waits forinstructions from across any one of the ports, preferably the serialport. The waiting period can be approximately a one second window inwhich time PC1 300 should respond with the prepared text programs. InStep S2606, if PC1 300 does not respond by sending a test program to NEB2 within the time window, flow advances to Step S2607 where the NEBenteres its normal operational mode.

When the test program instruction set from PC1 300 is received in StepS2606, the instruction set, which includes further test programs, isstored (in Step S2608) on NEB 2 in DRAM 220. In Step S2609, PC1 300activates the instruction set and NEB 2 executes each test programwithin the instruction set.

The test program instruction set may contain, in random order, testprograms which require NEB 2 to configure PC2 306 as a LAN peripheraldevice, or which require NEB 2 to configure PC2 306 as an SCSIperipheral device. In either case, after being configured, PC2 306 willrespond to each communication from NEB 2, usually by merely returningdata blocks sent by the NEB.

Briefly, in Step S2610 (FIG. 26B) NEB 2 configures PC2 306 as a LANperipheral and PC2 306 responds by sending a response to NEB 2 whicheffectively performs a LAN loopback test by returning the data which ithas received. NEB 2 will communicate with PC2 and receive simulatedprint job results. In Step S2611, the result of each block job is sentto PC1 300. PC1 300 determines if the test result is correct. In StepS2611, if it is determined by PC1 300 that the test result is incorrect,PC1 300 sends a re-scripted, branch test program (Step S2612) inaccordance with the test result received in Step S2611. However, if nofurther branch test program exists, then in Step S2612 PC1 300 will stopLAN testing and output an error signal.

Thus, in Step S2611, NEB 2 is tested for LAN communications. AssumingNEB 2 successfully passes each LAN communication test, flow advances toStep S2613 at which point PC2 306 is configured as an SCSI peripheraldevice and performs SCSI loopback tests by returning the data which ithas received. In Step S2614 the results of the tests are sent to PC1 300and if the results are incorrect, PC1 300 similarly sends a branch testin Step S2615 in accordance with the test result. Of course, if nofurther branch test exists to further test the peripheral communication,then PC1 300 stops the test, and outputs an error signal.

Assuming that NEB 2 successfully passes each SCSI communication test inStep S2614, then flow advances to Step S2616 at which point NEB 2requests further instructions from PC1 300. If PC1 300 returns withfurther instructions, flow returns to Step S2605, but if further testingis not necessary then NEB testing is ended.

In summary, a method for testing an interactive network board having aLAN interface and a test interface comprises the steps of applying powerto the board and reading a POST result which was executed out of boardROM via the test interface, and downloading a test program into theboard RAM via the test interface. The test program is then activated forexecution out of board RAM. The board may then be commanded to configurea peripheral device (through either the LAN or the SCSI interface) to bea LAN driver or an SCSI peripheral. The board then interacts with theLAN driver or SCSI peripheral in accordance with the test program.Results of the test program are then output via the test interface to atest computer which receives these test results. If certain tests fail,additional test programs may be scripted in accordance with the type offailure. The newly scripted test programs will be able to perform faultdetection and diagnosis, and these additionally scripted test programsmay then be downloaded to the board RAM from the PC1.

Once all of the tests are successfully concluded, it may be convenient(in the factory test environment) to flash the operational firmware intoEPROM 222. Specifically, the last step of a testing program may beutilized to load the requisite firmware image into the NEB EPROM 222prior to delivery (see section 4q above). The firmware flashed to EPROM222 may also include a unique MAC address for NEB 2.

In the past, MAC addresses were incorporated into circuit boards using adedicated PROM chip such as PROM 232. However, it has been found that ifthe MAC address is flashed into EPROM, the PROM chip is not required,while the MAC address can still be stored in a non-volatile way. (Ofcourse, as discussed in paragraph 4q, the MAC address could also beremotely flashed into the EPROM at the same time the RAM firmware imageis updated, after NEB 2 is coupled to the LAN.)

In Step S2617 of FIG. 26B, NEB testing has been completed and each boardmay be designated with its own individual identifier number, commonlyreferred to as a MAC address. Thus, in Step S2617 it is determinedwhetehr a ROM firmware image is to be stored in EPROM 222. If no imageis to be stored, testing ends. However, if an image is to be stored,flow advances to Step S2618 where the ROM image (with MAC address) isflashed to EPROM 222. At Step S2618 it may also be desirable to downloadother data normally stored in PROM 232, such as board revision number,data of manufacture, tester name, etc., together with the MAC address.

Two possible scenarios have been considered for flashing the ROMfirmware and MAC address to EPROM 222. In the first case the NEB 2 hasbeen pre-loaded with a sophisticated set of diagnostics for use inmanufacturing tests. This approach limits the amount of time needed todownload the specific tests since they will be already present in thefirmware. In this case, after the tests are successful the finalproduction version of the firmware is loaded into the board and flashedalong with the MAC address and other hardware related information suchas board revision, manufacturing data, and tester (Step S2618). In thesecond case the board will be built with the final production version ofthe firmware. In this case the board specific information area will beleft blank and only this area loaded and flashed after a successful testexecution in Step S2618.

In summary, a method for post-test loading of programmable firmware intoan interactive network board having a LAN interface comprises the stepof downloading a ROM firmware image (including the MAC address) to DRAM220 via the LAN interface. The integrity of the ROM image is thenconfirmed, and the board is commanded to electronically erase the EPROM.The EPROM is then flashed with the ROM image which includes the MACaddress, and the board is then re-booted from EPROM.

Thus, what has been described in detail above is an interactive networkcircuit board including structure and function for coupling a peripheralto a LAN so that the peripheral is a responsive interactive member ofthe LAN.

While the present invention has been described with respect to what isconsidered to be the preferred embodiments, it is to be understood thatthe present invention is not limited to the disclosed embodiments. Tothe contrary, the present invention is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims. The scope of the following claims is to beaccorded the broadest interpretation so as to encompass all suchmodifications and equivalent structures and functions.

What is claimed is:
 1. A method for preventing inadvertentre-programming of an EPROM, comprising the steps of:loading a ROMfirmware image into a RAM on an interactive network board; verifying theintegrity of the ROM firmware image in the RAM; receiving a command toload the EPROM; closing a switch in response to the command to load theEPROM so as to permit transfer of a load enable signal to a load enableinput on the EPROM, the load enable signal permitting the ROM firmwareimage to be loaded into the EPROM; erasing the EPROM; and loading theROM firmware image into the EPROM; wherein the step of closing theswitch is a two-step process which includes steps of (1) writing apredetermined bit pattern to a first address in order to generate afirst signal for closing the switch, and (2) reading from a secondaddress in order to generate a second signal for clocking the firstsignal to the switch so as to close the switch; and wherein, wheneverthe switch is open, the load enable input on the EPROM is substantiallygrounded.
 2. An apparatus for preventing inadvertent programming of anEPROM, comprising:an address bus; a data bus; an EPROM connected to saidaddress bus and to said data bus, said EPROM including a load enableinput; a switch for switchably providing a load enable signal to theload enable input of said EPROM, the load enable signal for permitting aROM firmware image to be loaded into said EPROM, the load enable inputof the EPROM being substantially grounded whenever said switch is open;a flip flop for controlling switching actuation of said switch; a latchresponsive to a first predetermined address on the address bus forlatching at least one bit from the data bus, said latch pre-loading theflip flop with the latched bit; means responsive to said latch latchingthe at least one bit for providing the load enable signal to saidswitch; a decoder responsive to a second predetermined address on saidaddress bus for clocking said flip flop; and a processor for outputtinga first predetermined bit pattern to the first predetermined address andfor accessing the second predetermined address so as to close saidswitch to permit the load enable signal to be provided to the loadenable input of said EPROM, for erasing said EPROM, and for loading theROM firmware image into said EPROM.
 3. An apparatus according to claim2, wherein said latch is responsive to a write to the firstpredetermined address.
 4. An apparatus according to claim 2, whereinsaid decoder is responsive to a read from the second predeterminedaddress.
 5. An apparatus according to claim 2, wherein said processor,after loading the ROM firmware image into said EPROM, outputs a secondpredetermined bit pattern, which is different from the firstpredetermined bit pattern, to the first predetermined address and whichagain accesses the second predetermined address.
 6. An apparatusaccording to claim 2, wherein the flip flop powers up such that saidswitch is prevented from providing the load enable signal to the loadenable input of said EPROM.
 7. An apparatus according to claim 2,wherein, upon power-up, said latch is set such that the flip flop is notpre-loaded.
 8. An apparatus according to claim 2, wherein said meansresponsive is comprised of a DC to DC converter and further includesmeans for discharge of the load enable signal.
 9. An apparatus accordingto claim 2, further comprising an NVRAM for non-volatively storing data,wherein the latch latches read and write data for the NVRAM.
 10. Anapparatus according to claim 9, wherein said latch latches a read/writecontrol bit, a clock bit, and a data bit for the NVRAM.
 11. An apparatusaccording to claim 10, wherein said latch utilizes a further bit toactivate the means responsive.
 12. An apparatus according to claim 2,wherein said EPROM is comprised by a flash EPROM.
 13. An apparatusaccording to claim 2, wherein said apparatus is disposed on aninteractive network board.
 14. An apparatus according to claim 2,wherein the apparatus is disposed on an interactive network boardcoupled to a printer.
 15. An interactive network board having an EPROMload protection circuit, comprising:a bi-directional interface disposedon the board; a LAN interface disposed on the board; a test interfacedisposed on the board; a RAM, disposed on the board, for storing a ROMfirmware image received over the LAN interface; an EPROM, disposed onthe board and responsive to an erase command and a load command, forstoring the ROM firmware image, said EPROM having a load enable inputfor receiving a load enable signal, the load enable signal forpermitting programming of said EPROM; a switch for switchably providingthe load enable signal to the load enable input of said EPROM; and aprocessor, disposed on the board, for processing executable files fromthe ROM firmware image stored in the EPROM, and wherein said processoris responsive to a LAN command from a remote LAN device to store a newROM firmware image in said RAM, to load the new ROM firmware image fromsaid RAM into said EPROM, and to reboot the interactive network boardfrom the new ROM firmware image in said EPROM, said processor causingsaid switch to close by (1) issuing a write command to a first addressin order to generate a first signal for closing said switch, and (2)issuing a read command to a second address in order to generate a secondsignal for clocking the first signal to the switch in order to close theswitch and to permit a load enable signal to be provided to the loadenable input of said EPROM, the load enable signal for permittingprogramming of the EPROM by loading the ROM firmware image from said RAMinto said EPROM; wherein the load enable input of said EPROM issubstantially grounded so as to prevent inadvertent programming of saidEPROM whenever the load enable signal is prevented from being providedto the load enable input of said EPROM.
 16. An interactive network boardaccording to claim 15, wherein the interactive network board is coupledto a printer.
 17. An interactive network board according to claim 15,wherein the RAM is a dynamic RAM.
 18. An interactive network boardaccording to claim 15, wherein said EPROM comprises a flash EPROM. 19.An interactive network board having a LAN interface, a bi-directionalinterface, and a test interface for loading a ROM firmware image into anEPROM disposed on the board, comprising:an address bus; a data bus; anEPROM connected to said address bus and to said data bus, said EPROMincluding a load enable input; a switch for switchably providing a loadenable signal to the load enable input of said EPROM, the load enablesignal for permitting loading of a ROM firmware image into said EPROM; aflip flop for controlling switching actuation of said switch; a latchresponsive to a first predetermined address on the address bus forlatching at least one bit from the data bus, said latch pre-loading theflip flop with the latched at least one bit; means responsive to saidlatch latching the at least one bit for providing the load enable signalto said switch; a decoder responsive to a second predetermined addresson said address bus for clocking said flip flop; and a processor foroutputting the predetermined bit pattern to the first address and foraccessing the second predetermined address so as to close said switch topermit the load enable signal to be provided to the load enable input ofsaid EPROM, for erasing said EPROM, and for loading the ROM firmwareimage into said EPROM, wherein said processor is responsive to a LANdownloaded command to load the ROM firmware image into a RAM and isresponsive to a LAN downloaded command to load said EPROM with the ROMfirmware image stored in the RAM; and wherein the load enable input issubstantially grounded whenever said switch is open so as to preventloading of a ROM firmware image into said EPROM.
 20. An apparatusaccording to claim 19, wherein said EPROM comprises a flash EPROM. 21.An interactive network board according to claim 19, wherein theinteractive network board is coupled to a printer.
 22. An apparatus forpreventing inadvertent programming of an EPROM, said apparatuscomprising:an address bus; a data bus; an EPROM connected to saidaddress bus and to said data bus, said EPROM including a load enableinput; a switch for switchably providing a load enable signal to theload enable input of said EPROM, the load enable signal for permitting aROM firmware image to be loaded into said EPROM; a flip flop forcontrolling switching actuation of said switch with an output thereof,said flip flop having an output terminal, a data terminal and a triggerterminal for clocking a signal at the data terminal to the outputterminal; a latch responsive to a first predetermined address on theaddress bus for latching at least one bit from the data bus so as togenerate a first signal, the first signal being provided to the dataterminal of said flip flop; a power generator for generating the loadenable signal and for providing the load enable signal to said switch,the load enable signal being generated in response to the first signalfrom said latch; a decoder responsive to a second predetermined addresson said address bus for generating a second signal, the second signalbeing provided to the trigger terminal of said flip flop so as to clocka signal at the data terminal to the output terminal; and a processorfor outputting a first predetermined bit pattern to the data bus to thefirst predetermined address so as to cause said latch to provide thefirst signal to the data terminal of said flip flop and to said powergenerator, and for accessing the second predetermined address so as toactivate said decoder to generate the second signal and to provide thesecond signal to the trigger terminal of said flip flop; wherein, whenthe second signal is applied to the trigger terminal of said flip flop,said flip flop transmits the first signal through to the outputterminal, the transferred first signal controlling actuation of saidswitch so as to permit the load enable signal to be provided from saidpower generator to the load enable input of said EPROM.
 23. An apparatusaccording to claim 20, wherein the apparatus is disposed on aninteractive network board coupled to a printer.
 24. A printer connectedto a local area network (LAN), comprising:a print engine which formsprinted images from print data received from the LAN; and an interactivenetwork board, interfaced to said print engine and to the LAN, forreceiving the print data from the LAN and for providing the print datato said print engine, said interactive network board comprising:anaddress bus; a data bus; an EPROM connected to said address bus and tosaid data bus, said EPROM including a load enable input; a switch forswitchably providing a load enable signal to the load enable input ofsaid EPROM, the load enable signal for permitting a ROM firmware imageto be loaded into said EPROM, the load enable input of the EPROM beingsubstantially grounded whenever said switch is open; a flip flop forcontrolling switching actuation of said switch; a latch responsive to afirst predetermined address on the address bus for latching at least onebit from the data bus, said latch pre-loading the flip flop with thelatched bit; means responsive to said latch latching the at least onebit for providing the load enable signal to said switch; a decoderresponsive to a second predetermined address on said address bus forclocking said flip flop; and a processor (1) for outputting a firstpredetermined bit pattern to the first predetermined address and foraccessing the second predetermined address so as to close said switch topermit the load enable signal to be provided to the load enable input ofsaid EPROM, for erasing said EPROM, and for loading the ROM firmwareimage into said EPROM, and (2) for executing a print server program totransmit the print data received from the LAN to said print engine. 25.A printer connected to a local area network (LAN), comprising:a printengine which forms printed images from print data received from the LAN;and an interactive network board, interfaced to said print engine and tothe LAN, for receiving the print data from the LAN and for providing theprint data to said print engine, said interactive network boardcomprising:a bi-directional interface disposed on the board; a LANinterface disposed on the board; a test interface disposed on the board;a RAM, disposed on the board, for storing a ROM firmware image receivedover the LAN interface; an EPROM, disposed on the board and responsiveto an erase command and a load command, for storing the ROM firmwareimage, said EPROM having a load enable input for receiving a load enablesignal, the load enable signal for permitting programming of said EPROM;a switch for switchably providing the load enable signal to the loadenable input of said EPROM; and a processor, disposed on the board, forprocessing executable files from the ROM firmware image stored in theEPROM and for executing a print server program to transmit the printdata to said print engine, and wherein said processor is responsive to aLAN command from a remote LAN device to store a new ROM firmware imagein said RAM, to load the new ROM firmware image from said RAM into saidEPROM, and to reboot the interactive network board from the new ROMfirmware image in said EPROM, said processor causing said switch toclose by (1) issuing a write command to a first address in order togenerate a first signal for closing said switch, and (2) issuing a readcommand to a second address in order to generate a second signal forclocking the first signal to the switch in order to close the switch andto permit a load enable signal to be provided to the load enable inputof said EPROM, the load enable signal for permitting programming of theEPROM by loading the ROM firmware image from said RAM into said EPROM;wherein the load enable input of said EPROM is substantially grounded soas to prevent inadvertent programming of said EPROM whenever the loadenable signal is prevented from being provided to the load enable inputof said EPROM.
 26. A printer connected to a local area network (LAN),comprising:a print engine which forms printed images from print datareceived from the LAN; and an interactive network board, interfaced tosaid print engine and to the LAN, for receiving the print data from theLAN and for providing the print data to said print engine, saidinteractive network board comprising:an address bus; a data bus; anEPROM connected to said address bus and to said data bus, said EPROMincluding a load enable input; a switch for switchably providing a loadenable signal to the load enable input of said EPROM, the load enablesignal for permitting loading of a ROM firmware image into said EPROM; aflip flop for controlling switching actuation of said switch; a latchresponsive to a first predetermined address on the address bus forlatching at least one bit from the data bus, said latch pre-loading theflip flop with the latched at least one bit; means responsive to saidlatch latching the at least one bit for providing the load enable signalto said switch; a decoder responsive to a second predetermined addresson said address bus for clocking said flip flop; and a processor (1) forexecuting a print server program to transmit the print data receivedfrom the LAN to said print engine, and (2) for outputting thepredetermined bit pattern to the first address and for accessing thesecond predetermined address so as to close said switch to permit theload enable signal to be provided to the load enable input of saidEPROM, for erasing said EPROM, and for loading the ROM firmware imageinto said EPROM, wherein said processor is responsive to a LANdownloaded command to load the ROM firmware image into a RAM and isresponsive to a LAN downloaded command to load said EPROM with the ROMfirmware image stored in the RAM; and wherein the load enable input issubstantially grounded whenever said switch is open so as to preventloading of a ROM firmware image into said EPROM.
 27. A printer connectedto a local area network (LAN), comprising:a print engine which formsprinted images from print data received from the LAN; and an interactivenetwork board, interfaced to said print engine and to the LAN, forreceiving the print data from the LAN and for providing the print datato said print engine, said interactive network board comprising:anaddress bus; a data bus; an EPROM connected to said address bus and tosaid data bus, said EPROM including a load enable input; a switch forswitchably providing a load enable signal to the load enable input ofsaid EPROM, the load enable signal for permitting a ROM firmware imageto be loaded into said EPROM; a flip flop for controlling switchingactuation of said switch with an output thereof, said flip flop havingan output terminal, a data terminal and a trigger terminal for clockinga signal at the data terminal to the output terminal; a latch responsiveto a first predetermined address on the address bus for latching atleast one bit from the data bus so as to generate a first signal, thefirst signal being provided to the data terminal of said flip flop; apower generator for generating the load enable signal and for providingthe load enable signal to said switch, the load enable signal beinggenerated in response to the first signal from said latch; a decoderresponsive to a second predetermined address on said address bus forgenerating a second signal, the second signal being provided to thetrigger terminal of said flip flop so as to clock a signal at the dataterminal to the output terminal; and a processor (1) for executing aprint server program to transmit the print data received from the LAN tosaid print engine, and (2) for outputting a first predetermined bitpattern to the data bus to the first predetermined address so as tocause said latch to provide the first signal to the data terminal ofsaid flip flop and to said power generator, and for accessing the secondpredetermined address so as to activate said decoder to generate thesecond signal and to provide the second signal to the trigger terminalof said flip flop; wherein, when the second signal is applied to thetrigger terminal of said flip flop, said flip flop transmits the firstsignal through to the output terminal, the transferred first signalcontrolling actuation of said switch so as to permit the load enablesignal to be provided from said power generator to the load enable inputof said EPROM.